50278 + Interview Questions in Physics

1.	Find the co-ordinates of the centre of mass of the lamina, shown in figure.
Answer» Find the co-ordinates of the centre of mass of the lamina, shown in figure.

Discussion

2.	A body strike a smooth horizontal surface with speed u at an inclination of angle theta . If coefficient of restitution is e ,than find the ratio of horizontal range between two consecutive motion of body? 1. 1/e 2.1/e2cos(theta) 3.1/esin(theta) 4.e
Answer» A body strike a smooth horizontal surface with speed u at an inclination of angle theta . If coefficient of restitution is e ,than find the ratio of horizontal range between two consecutive motion of body? 1. 1/e 2.1/e2cos(theta) 3.1/esin(theta) 4.e

Discussion

3.	What is centripetal and centrifugal force. What is difference among centripetal and centrifugal?
Answer» What is centripetal and centrifugal force. What is difference among centripetal and centrifugal?

Discussion

4.	A bulb emits light of wave length 396 nm. The bulb is rated as 100 watt and 10% of the energy is emitted as light. How many photons are emitted by bulb per second?
Answer» A bulb emits light of wave length 396 nm. The bulb is rated as 100 watt and 10% of the energy is emitted as light. How many photons are emitted by bulb per second?

Discussion

5.	47.A small conducting spherical shell with inner radius a and outer radius b is concentric with a larger conducting spherical shell with inner radius c and outer radius d . The inner shell has total charge +2q and outer shell has charge +4q. Calculate the electric field in terms of q and r from common centre of two shells for
Answer» 47.A small conducting spherical shell with inner radius a and outer radius b is concentric with a larger conducting spherical shell with inner radius c and outer radius d . The inner shell has total charge +2q and outer shell has charge +4q. Calculate the electric field in terms of q and r from common centre of two shells for

Discussion

6.	An infinitely long non conducting cylinder of inner radius 5 cm and outer radius 7 cm has uniform volume charge density 8.85 \ast10^-9 .the magnitude of electric field at a distance 10 cm from axis of cylinder is ?
Answer» An infinitely long non conducting cylinder of inner radius 5 cm and outer radius 7 cm has uniform volume charge density 8.85 \ast10^-9 .the magnitude of electric field at a distance 10 cm from axis of cylinder is ?

Discussion

7.	Five rods of same dimensions are arranged as shown in the figure. They have thermal conductivities K1,K2,K3,K4 and K5. When points A and B are maintained at different temperatures, no heat flows through the central rod if
Answer» Five rods of same dimensions are arranged as shown in the figure. They have thermal conductivities $K_{1}, K_{2}, K_{3}, K_{4} a n d K_{5}$ . When points A and B are maintained at different temperatures, no heat flows through the central rod if

Discussion

8.	Evaluate the integral ∫π20sinx dx
Answer» Evaluate the integral $\int_{0}^{\frac{π}{2}} sin x d x$

Discussion

9.	The wavelength of the carrier waves in a modern optical fibre communication network is close to
Answer» The wavelength of the carrier waves in a modern optical fibre communication network is close to

Discussion

10.	When a certain photosensitive surface is illuminated with monochromatic light of frequency ν, the stopping potential for the photo current is −V0/2. When the surface is illuminated by monochromatic light of frequency ν/2, the stopping potential is −V0. The threshold frequency for photoelectric emission is:
Answer» When a certain photosensitive surface is illuminated with monochromatic light of frequency $ν$ , the stopping potential for the photo current is $- V_{0} / 2$ . When the surface is illuminated by monochromatic light of frequency $ν / 2$ , the stopping potential is $- V_{0}$ . The threshold frequency for photoelectric emission is:

Discussion

11.	In Gauss law can the conductor be hollow or solid?
Answer» In Gauss law can the conductor be hollow or solid?

Discussion

12.	For the resultant of two vectors to be maximum, the angle between them should be
Answer» For the resultant of two vectors to be maximum, the angle between them should be

Discussion

13.	The variation of magnetic susceptibility (χ) with absolute temperature T
Answer» The variation of magnetic susceptibility $(χ)$ with absolute temperature T

Discussion

14.	A thin rod of mass M and length L is bent in semicircle as shown in figure. The gravitational force on a particle with mass m at O, the centre of curvature is...
Answer» A thin rod of mass M and length L is bent in semicircle as shown in figure. The gravitational force on a particle with mass m at O, the centre of curvature is...

Discussion

15.	10.Find the charge on 3 micro farad , 4 micorfarad and 5 micro farad. Also find the potential of point C and D.
Answer» 10.Find the charge on 3 micro farad , 4 micorfarad and 5 micro farad. Also find the potential of point C and D.

Discussion

16.	A semicircular disc is cut out from a square sheet of side 20 cm as shown in the figure. What is the distance of the centre of mass of the new shape from y− axis ? Consider the material to be of uniform density and the origin to be at point O.
Answer» A semicircular disc is cut out from a square sheet of side $20 cm$ as shown in the figure. What is the distance of the centre of mass of the new shape from $y -$ axis ? Consider the material to be of uniform density and the origin to be at point $O$ .

Discussion

17.	33. AB has ZnS type structure. What will be interionic distance between A+ and B- if lattice constant of AB is 200 pm?
Answer» 33. AB has ZnS type structure. What will be interionic distance between A+ and B- if lattice constant of AB is 200 pm?

Discussion

18.	Which of the following reactions is associated with the most negative change in entropy?
Answer» Which of the following reactions is associated with the most negative change in entropy?

Discussion

19.	At a point on a level plane, a vertical tower subtends and angle α and a pole of height h meters at the top of the tower subtends an angle β. Show that the height of the tower is h sinβ.cosαcos(α+β)
Answer» At a point on a level plane, a vertical tower subtends and angle $α$ and a pole of height h meters at the top of the tower subtends an angle $β$ . Show that the height of the tower is h $\frac{s i n β . c o s α}{c o s (α + β)}$

Discussion

20.	Consider the truss shown in figure below:The degree of static indeterminacy of the above shown truss is0
Answer» Consider the truss shown in figure below: The degree of static indeterminacy of the above shown truss is 0

Discussion

21.	8181J(4)(3)24In given figure, if acceleration of 2 kg and 3 kg area, respectively then relation between a18.and a2andisT2(1) a= 2a2(2) 2a, 3a23a, 2a2 TT(4) 2a, a2113 kgT2-24T 322 kg19. A particle of mass m is moving with constant speedv in a circular path of radius r. The power delivered
Answer» 8181J(4)(3)24In given figure, if acceleration of 2 kg and 3 kg area, respectively then relation between a18.and a2andisT2(1) a= 2a2(2) 2a, 3a23a, 2a2 TT(4) 2a, a2113 kgT2-24T 322 kg19. A particle of mass m is moving with constant speedv in a circular path of radius r. The power delivered

Discussion

22.	In the given circuit, in steady state, find the potential differences across points A and B .
Answer» In the given circuit, in steady state, find the potential differences across points $A$ and $B$ .

Discussion

23.	A system is given 400 cal of heat and 1000 J of work done by the system, then the change in internal energy of the system will be
Answer» A system is given $400 cal$ of heat and $1000 J$ of work done by the system, then the change in internal energy of the system will be

Discussion

24.	A rod PQ of mass m and resistance r is moving on two fixed, resistanceless, smooth conducting rails, closed by resistances R1 and R2 as shown in the figure. Find the current in the rod at the instant when its velocity is v.
Answer» A rod $P Q$ of mass $m$ and resistance $r$ is moving on two fixed, resistanceless, smooth conducting rails, closed by resistances $R_{1}$ and $R_{2}$ as shown in the figure. Find the current in the rod at the instant when its velocity is $v$ .

Discussion

25.	The critical load Pcr for the bar spring system is ?
Answer» The critical load $P_{c r}$ for the bar spring system is ?

Discussion

26.	four particles of masses m, 2m, 3m and 4m are kept in sequence at the corners of a square of side a. The magnitude of gravitational force acting on a particle of mass m placed at the centre of the square will be
Answer» four particles of masses m, 2m, 3m and 4m are kept in sequence at the corners of a square of side a. The magnitude of gravitational force acting on a particle of mass m placed at the centre of the square will be

Discussion

27.	The energy levels of the hydrogen spectrum is shown in figure. There are some transitions A, B, C, D and E. Transition A, B and C respectively represent
Answer» The energy levels of the hydrogen spectrum is shown in figure. There are some transitions A, B, C, D and E. Transition A, B and C respectively represent

Discussion

28.	Q) A CHARGE q IS DISTRIBUTED UNIFORMLY OVER A RING OF RADIUS a. CALCULATE THE ELECTRIC FIELD INTENSITY AT A DISTANCE x ON ITS AXIS FROM THE CENTRE. CAN DISTRIBUTION OF CHARGE OVER THE RING BE IGNORED?
Answer» Q) A CHARGE q IS DISTRIBUTED UNIFORMLY OVER A RING OF RADIUS a. CALCULATE THE ELECTRIC FIELD INTENSITY AT A DISTANCE x ON ITS AXIS FROM THE CENTRE. CAN DISTRIBUTION OF CHARGE OVER THE RING BE IGNORED?

Discussion

29.	How to know sp2 hybridization
Answer» How to know sp2 hybridization

Discussion

30.	A glass sphere (refractive index =1.5) with a radius of 15cm has a tiny air bubble 5cm above its centre. The sphere is viewed looking down along the extended radius containing the bubble. What is the apparent depth of the bubble below the surface of the sphere?
Answer» A glass sphere (refractive index =1.5) with a radius of 15cm has a tiny air bubble 5cm above its centre. The sphere is viewed looking down along the extended radius containing the bubble. What is the apparent depth of the bubble below the surface of the sphere?

Discussion

31.	Taylor's tool life equation is used to estimate the life of a batch of identical HSS twist drills by drilling through holes at constant feed in 20 mm thick mild steel plates. In test 1, a drill lasted 300 holes at 150 rpm while in test 2, another drill lasted 200 holes at 300 rpm. The maximum number of holes that can be made by another drill from the above batch at 200 rpm is (correct to two decimal places.)
Answer» Taylor's tool life equation is used to estimate the life of a batch of identical HSS twist drills by drilling through holes at constant feed in 20 mm thick mild steel plates. In test 1, a drill lasted 300 holes at 150 rpm while in test 2, another drill lasted 200 holes at 300 rpm. The maximum number of holes that can be made by another drill from the above batch at 200 rpm is (correct to two decimal places.)

Discussion

32.	The electric current in a circuit is given by i=i0(tπ) for some time. Calculate the rms current for the period t=0 to t=π.
Answer» The electric current in a circuit is given by $i = i_{0} (\frac{t}{π})$ for some time. Calculate the $r m s$ current for the period $t = 0$ to $t = π$ .

Discussion

33.	A diode is connected to 220 V(rms) AC in series with a capacitor, as shown in figure. The voltage across the capacitor is
Answer» A diode is connected to $220 V$ (rms) AC in series with a capacitor, as shown in figure. The voltage across the capacitor is

Discussion

34.	Obtain the expression for magnetic energy stored in a solenoid in terms of its magnetic field B, area of cross section A, and length l.
Answer» Obtain the expression for magnetic energy stored in a solenoid in terms of its magnetic field B, area of cross section A, and length l.

Discussion

35.	If an object is placed at A(OA>f); where f is the local length of the lens, the image is formed at B. A perpendicular is erected at O and C is choosen on it such that the ∠BCA is a right angle. Then the value of f will be:
Answer» If an object is placed at $A (O A > f)$ ; where $f$ is the local length of the lens, the image is formed at $B$ . A perpendicular is erected at $O$ and $C$ is choosen on it such that the $∠ B C A$ is a right angle. Then the value of $f$ will be:

Discussion

36.	When an object is kept over a surface then two forces act. First is the wight f the object and Second are the reaction ie normal forces. One normal force would be in a direction opposite to the direction of weight and the other would be opposite to it. Will the magnitude of both the normal forces be same?
Answer» When an object is kept over a surface then two forces act. First is the wight f the object and Second are the reaction ie normal forces. One normal force would be in a direction opposite to the direction of weight and the other would be opposite to it. Will the magnitude of both the normal forces be same?

Discussion

37.	In a common emitter transistor, the current gain is 80. What is the change in collector current, when the change in base current is 250 mA
Answer» In a common emitter transistor, the current gain is 80. What is the change in collector current, when the change in base current is 250 mA

Discussion

38.	A girl is riding a bike with the speed of 100 km/hr on an inclined plane of 37 degree. The rain is falling with speed of 50 km/hr at an angle of 53 degree with the horizontal. At what angle with the vertical the girl should open umbrella to protect herself from the rain?
Answer» A girl is riding a bike with the speed of 100 km/hr on an inclined plane of 37 degree. The rain is falling with speed of 50 km/hr at an angle of 53 degree with the horizontal. At what angle with the vertical the girl should open umbrella to protect herself from the rain?

Discussion

39.	A Light source that radiates E Joules of energy per secondis kept at the centre of a hemisphere. How much energy will the hemisphere receive? Energy = __
Answer» A Light source that radiates E Joules of energy per secondis kept at the centre of a hemisphere. How much energy will the hemisphere receive? Energy = __

39.

A Light source that radiates E Joules of energy per secondis kept at the centre of a hemisphere. How much energy will the hemisphere receive? Energy = __

Answer»

A Light source that radiates E Joules of energy per secondis kept at the centre of a hemisphere. How much energy will the hemisphere receive?

Energy = __

Discussion

40.	A reversed Carnot cycle refrigerator maintains a temperature of −5∘C. The ambient air temperature is 35∘C. The heat gained by the refrigerator at a continuous rate is 2.5 kJ/s. The power (in watts) required to pump this heat out continuously is
Answer» A reversed Carnot cycle refrigerator maintains a temperature of $- 5^{\circ} C$ . The ambient air temperature is $35^{\circ} C$ . The heat gained by the refrigerator at a continuous rate is 2.5 kJ/s. The power (in watts) required to pump this heat out continuously is

Discussion

41.	How much (in times) faster than its normal rate should the earth be rotating about its axis so that the weight of the body at the equator becomes zero ? (R=6.4×106 m, g=10 m/s2)
Answer» How much (in times) faster than its normal rate should the earth be rotating about its axis so that the weight of the body at the equator becomes zero $?$ $(R = 6.4 \times 10^{6} m, g = 10$ ${m/s}^{2})$

Discussion

42.	A body describes simple harmonic motion with an amplitude of 5 cm and a period of 0.2 s. Find the acceleration and velocity of the body when the displacement is (a) 5 cm (b) 3 cm (c) 0 cm.
Answer» A body describes simple harmonic motion with an amplitude of 5 cm and a period of 0.2 s. Find the acceleration and velocity of the body when the displacement is (a) 5 cm (b) 3 cm (c) 0 cm.

Discussion

43.	Who among the following gave first the experimental value of G
Answer» Who among the following gave first the experimental value of G

Discussion

44.	Find the average velocity of tip of the minute hand of an analog watch when it turn for 30 minutes.
Answer» Find the average velocity of tip of the minute hand of an analog watch when it turn for $30 minutes$ .

Discussion

45.	Two uniform and identical rectangular plates of dimensions a × 4a are arranged as shown in the figure to form a tee (T). The distance of the centre of mass of the system from the bottom of the tee (shown by dotted lines) is
Answer» Two uniform and identical rectangular plates of dimensions a × 4a are arranged as shown in the figure to form a tee (T). The distance of the centre of mass of the system from the bottom of the tee (shown by dotted lines) is

45.

Two uniform and identical rectangular plates of dimensions a × 4a are arranged as shown in the figure to form a tee (T). The distance of the centre of mass of the system from the bottom of the tee (shown by dotted lines) is

Answer»

Two uniform and identical rectangular plates of dimensions a × 4a are arranged as shown in the figure to form a tee (T). The distance of the centre of mass of the system from the bottom of the tee (shown by dotted lines) is

Discussion

46.	A body of mass 10 kg is dropped to the ground from a height of 10 metres. The work done by the gravitational force is g=9.8 m/sec2
Answer» A body of mass 10 kg is dropped to the ground from a height of 10 metres. The work done by the gravitational force is $g = 9.8 m / s e c^{2}$

Discussion

47.	A body suspended on a spring balance inside the spaceship weighs W when ship is at rest at the earth's equator. If W0 is the weight of the body in the stationary ship when we assume earth not rotating about its axis and ω is the angular velocity of rotation of earth then weight W is
Answer» A body suspended on a spring balance inside the spaceship weighs $W$ when ship is at rest at the earth's equator. If $W_{0}$ is the weight of the body in the stationary ship when we assume earth not rotating about its axis and $ω$ is the angular velocity of rotation of earth then weight $W$ is

Discussion

48.	Following data correspond to an orthogonal Turning of a 100 mm diameter rod on a lathe. Rake angle: +15°; Uncut chip thickness 0.5 mm, nominal chip thickness after the cut 1.25 mm. The shear angle (in degrees) for this process is (correct to two decimal places).
Answer» Following data correspond to an orthogonal Turning of a 100 mm diameter rod on a lathe. Rake angle: +15°; Uncut chip thickness 0.5 mm, nominal chip thickness after the cut 1.25 mm. The shear angle (in degrees) for this process is (correct to two decimal places).

Discussion

49.	70.Force between 2 charged particle is 20N. Both charged particles are separated at distance of 0.60m if both the charges are moving towards each other by 0.15m then calculate the force between charged particles.
Answer» 70.Force between 2 charged particle is 20N. Both charged particles are separated at distance of 0.60m if both the charges are moving towards each other by 0.15m then calculate the force between charged particles.

Discussion

50.	An RLC circuit with R=100Ω is connected across ac source of 200V and angular frequency 300 rad/s. When the only capacitance is removed, the current lags behind voltage by 60∘. When only inductance is removed, the current leads the voltage by 60∘. The current in the circuit is___(in Ampere)
Answer» An RLC circuit with $R = 100 Ω$ is connected across ac source of 200V and angular frequency 300 rad/s. When the only capacitance is removed, the current lags behind voltage by $60^{\circ}$ . When only inductance is removed, the current leads the voltage by $60^{\circ}$ . The current in the circuit is___(in Ampere)

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Find the co-ordinates of the centre of mass of the lamina, shown in figure.

A body strike a smooth horizontal surface with speed u at an inclination of angle theta . If coefficient of restitution is e ,than find the ratio of horizontal range between two consecutive motion of body? 1. 1/e 2.1/e2cos(theta) 3.1/esin(theta) 4.e

What is centripetal and centrifugal force. What is difference among centripetal and centrifugal?

A bulb emits light of wave length 396 nm. The bulb is rated as 100 watt and 10% of the energy is emitted as light. How many photons are emitted by bulb per second?

An infinitely long non conducting cylinder of inner radius 5 cm and outer radius 7 cm has uniform volume charge density 8.85 \ast10^-9 .the magnitude of electric field at a distance 10 cm from axis of cylinder is ?

Five rods of same dimensions are arranged as shown in the figure. They have thermal conductivities K1,K2,K3,K4 and K5. When points A and B are maintained at different temperatures, no heat flows through the central rod if

Evaluate the integral ∫π20sinx dx

The wavelength of the carrier waves in a modern optical fibre communication network is close to

In Gauss law can the conductor be hollow or solid?

For the resultant of two vectors to be maximum, the angle between them should be

The variation of magnetic susceptibility (χ) with absolute temperature T

A thin rod of mass M and length L is bent in semicircle as shown in figure. The gravitational force on a particle with mass m at O, the centre of curvature is...

10.Find the charge on 3 micro farad , 4 micorfarad and 5 micro farad. Also find the potential of point C and D.

A semicircular disc is cut out from a square sheet of side 20 cm as shown in the figure. What is the distance of the centre of mass of the new shape from y− axis ? Consider the material to be of uniform density and the origin to be at point O.

33. AB has ZnS type structure. What will be interionic distance between A+ and B- if lattice constant of AB is 200 pm?

Which of the following reactions is associated with the most negative change in entropy?

At a point on a level plane, a vertical tower subtends and angle α and a pole of height h meters at the top of the tower subtends an angle β. Show that the height of the tower is h sinβ.cosαcos(α+β)

Consider the truss shown in figure below:The degree of static indeterminacy of the above shown truss is0

8181J(4)(3)24In given figure, if acceleration of 2 kg and 3 kg area, respectively then relation between a18.and a2andisT2(1) a= 2a2(2) 2a, 3a23a, 2a2 TT(4) 2a, a2113 kgT2-24T 322 kg19. A particle of mass m is moving with constant speedv in a circular path of radius r. The power delivered

In the given circuit, in steady state, find the potential differences across points A and B .

A system is given 400 cal of heat and 1000 J of work done by the system, then the change in internal energy of the system will be

A rod PQ of mass m and resistance r is moving on two fixed, resistanceless, smooth conducting rails, closed by resistances R1 and R2 as shown in the figure. Find the current in the rod at the instant when its velocity is v.

The critical load Pcr for the bar spring system is ?

four particles of masses m, 2m, 3m and 4m are kept in sequence at the corners of a square of side a. The magnitude of gravitational force acting on a particle of mass m placed at the centre of the square will be

The energy levels of the hydrogen spectrum is shown in figure. There are some transitions A, B, C, D and E. Transition A, B and C respectively represent

Q) A CHARGE q IS DISTRIBUTED UNIFORMLY OVER A RING OF RADIUS a. CALCULATE THE ELECTRIC FIELD INTENSITY AT A DISTANCE x ON ITS AXIS FROM THE CENTRE. CAN DISTRIBUTION OF CHARGE OVER THE RING BE IGNORED?

How to know sp2 hybridization

A glass sphere (refractive index =1.5) with a radius of 15cm has a tiny air bubble 5cm above its centre. The sphere is viewed looking down along the extended radius containing the bubble. What is the apparent depth of the bubble below the surface of the sphere?

The electric current in a circuit is given by i=i0(tπ) for some time. Calculate the rms current for the period t=0 to t=π.

A diode is connected to 220 V(rms) AC in series with a capacitor, as shown in figure. The voltage across the capacitor is

Obtain the expression for magnetic energy stored in a solenoid in terms of its magnetic field B, area of cross section A, and length l.

If an object is placed at A(OA&gt;f); where f is the local length of the lens, the image is formed at B. A perpendicular is erected at O and C is choosen on it such that the ∠BCA is a right angle. Then the value of f will be:

In a common emitter transistor, the current gain is 80. What is the change in collector current, when the change in base current is 250 mA

A girl is riding a bike with the speed of 100 km/hr on an inclined plane of 37 degree. The rain is falling with speed of 50 km/hr at an angle of 53 degree with the horizontal. At what angle with the vertical the girl should open umbrella to protect herself from the rain?

A Light source that radiates E Joules of energy per secondis kept at the centre of a hemisphere. How much energy will the hemisphere receive? Energy = __

A reversed Carnot cycle refrigerator maintains a temperature of −5∘C. The ambient air temperature is 35∘C. The heat gained by the refrigerator at a continuous rate is 2.5 kJ/s. The power (in watts) required to pump this heat out continuously is

How much (in times) faster than its normal rate should the earth be rotating about its axis so that the weight of the body at the equator becomes zero ? (R=6.4×106 m, g=10 m/s2)

A body describes simple harmonic motion with an amplitude of 5 cm and a period of 0.2 s. Find the acceleration and velocity of the body when the displacement is (a) 5 cm (b) 3 cm (c) 0 cm.

Who among the following gave first the experimental value of G

Find the average velocity of tip of the minute hand of an analog watch when it turn for 30 minutes.

Two uniform and identical rectangular plates of dimensions a × 4a are arranged as shown in the figure to form a tee (T). The distance of the centre of mass of the system from the bottom of the tee (shown by dotted lines) is

A body of mass 10 kg is dropped to the ground from a height of 10 metres. The work done by the gravitational force is g=9.8 m/sec2

A body suspended on a spring balance inside the spaceship weighs W when ship is at rest at the earth's equator. If W0 is the weight of the body in the stationary ship when we assume earth not rotating about its axis and ω is the angular velocity of rotation of earth then weight W is

Following data correspond to an orthogonal Turning of a 100 mm diameter rod on a lathe. Rake angle: +15°; Uncut chip thickness 0.5 mm, nominal chip thickness after the cut 1.25 mm. The shear angle (in degrees) for this process is (correct to two decimal places).

70.Force between 2 charged particle is 20N. Both charged particles are separated at distance of 0.60m if both the charges are moving towards each other by 0.15m then calculate the force between charged particles.

An RLC circuit with R=100Ω is connected across ac source of 200V and angular frequency 300 rad/s. When the only capacitance is removed, the current lags behind voltage by 60∘. When only inductance is removed, the current leads the voltage by 60∘. The current in the circuit is___(in Ampere)

If an object is placed at A(OA>f); where f is the local length of the lens, the image is formed at B. A perpendicular is erected at O and C is choosen on it such that the ∠BCA is a right angle. Then the value of f will be: