1.

Find the focal length of double convex lens with refrative index (n)1.5,r1=20cm,r2=20m​

Answer»

Answer:

Lens maker formula

1/F=(u−1)[1∣R

1

−1∣R

2

]

Where F is focal LENGTH of lens

U is the refractive index of lens with respect to MEDIUM

R

1

and R

2

are the RADIUS of curvature of both curve surface of lens

given

n=1.5

So,U=n relative to vacuum or air

u=n/1=1.5/1=1.5

R

1

=−30cm

R

2

=60cm

So,

1/F=(1.5−1){

−30

1

−

60

1

}

F

1

=(0.5)(

−30

1

−

60

−

)

F=

−0.025

1


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