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• Food preservation is the process of treating and handling food to stop or slow down spoilage. 
• It provides food availability throughout the year. 
• Food preservation stop the food wastage. 
• If food is not preserved properly, it can attack by microorganisms that lead to spoilage of food.

Recipe: A list of materials used for preparing dishes.

• Preparation of food is an art. It is prepared in different ways. 
• There should be no loss of nutrients while cooking. 
• Some food items are delicious in certain food preparing methods. 
• The taste of the food depends on its ingredients and the method of preparation also. So that we use different methods for preparing the food.

• Steaming process is a method of preparation of food. 
• In this process boiling of water causes it to vaporize into steam. 
• The steam carries heat to the food, thus cooking the food. 
• Idli, cake, egg is cooked by steaming process.

Fermentation: A process in which an agent causes an organic substance to break down into a simpler substance.

The correct answer is C) Steaming.

“INDIAN SPICES”: Spices are aromatic parts of tropical plants traditionally used to add flavour to the food. Spices come from the bark roots of certain plants, leaves, flowers or stems of plants primarily used for flavouring, colouring or preserving food. Spices are included in a variety of Indian dishes: cardamom, black pepper, curry leaves, fenugreek, fennel, ajwain, bay leaves, cumin, coriander seeds, turmeric, cloves, ginger, nutmeg and cinnamon.

PuIses: PuIses are the dried seeds of the legume plants. Ex: Beans. 

Roasting: To cook food in an oven or over a fire.

Carving: Making of different types of designs and decorations with vegetables and fruits.

Some people make different types of designs and decorations with vegetables and fruits. This is called vegetable carving.

The correct answer is D) Potato

Making of different types of designs and decorations with vegetables is called vegetable carving.

• Food is precious – Don’t waste food. 
• Think for those who are hungry before throwing your food into the dustbin. 
• Conserve food so that no one dies out of hunger. 
• Today’s wastage is tomorrow’s shortage.

Natural preservatives

A – 4 

B – 1 

C – 2 

D – 5 

E – 3

Honeybees/animals

Sugar syrup or honey is used in the canning and freezing of fruits to improve its flavour and to preserve its natural colour and taste.

Given : 

Wavelength (λ) = 580 nm 

To find : 

Frequency (ν), Wave number \(\bar v\) 

Formulae :

\(v\) = \(\frac{c}{\lambda}\), \(\bar v\) = \(\frac{1}{\lambda}\) 

Calculation : 

Wavelength of yellow light (λ) = 580 nm = 580 × 10^-9 m [1 nm = 10^-9m]

We know that frequency (ν) is related to wavelength as :

ν = \(\frac{c}{\lambda}\) 

Where, c, velocity of light = 3.0 × 10^-8 m s^-1

∴ ν = \(\frac{3.0\times 10^8 ms^{-1}}{580\times 10^{-9}m}\) 

= 5.17 × 10¹⁴ s^-1

Again, 

Wave number,

\(\bar v\) = \(\frac{1}{\lambda}\)

= \(\frac{1}{580\times 10^{-9}m}\) 

= 1.72 x 10⁶ m^-1

Frequency = 5.17 × 10¹⁴s^-1 and wave number = 1.72 × 10⁶m^-1

(a) λ = 6 nm = 6 x 10^-9 m

Frequency, v = C/λ = {3 x 10⁸ m/sec}/{616 x 10^-9} m

= 4.87 x 10^-14 s^-1

(b) Distance travelled by the radiation in 30 s

= 3 x 10⁸ m/sec x 30 sec

= 9.0 x 10⁹ m

(c) E = hv

= 6.626 x 10^-34 Js x 4.87 x 10¹⁴

= 32.27 x 10^-20 J

(d) Number of quanta present = 6.2 x 10¹⁸

(a) A switch is the source of electric current in a circuit. 

Rechargable batteries can be recharged by providing them appropriate current.

(a) A device that is used to break an electric circuit is called switch.
(b) An electric cell has two terminals.

Activity you perform                                               Device
Get light                                                                 Torch
Heat water                                                             Geyser/immersion rod
Make toast                                                             Toaster
Cook food                                                               Heater/microwave
Listen to music                                                       CD player/radio/i-pod

(a) Electric current can flow through metals. (True)
(b) Instead of metal wires, a jute string can be used to make a circuit. (False)
(c) Electric current can pass through a sheet of thermo Col. (False)

Eraser is insulator, so circuit will not complete. As a result the bulb will not glow.

(c) A plastic clip 

The handle of screw is made up of insulator, which does allow to current to flow. That is why the bulb is not glowing.

No the bulb will not glow in this circuit because the switch is open and the circuit is incomplete.

Since the object allows current to flow and completes the circuit and makes bulb to glow. It means the object is a conductor of electricity.

Z=19   1s² ,2s² ,2p⁶ ,3s² ,3p⁶ ,4s¹    

P-4th,       G-1st

Z=35   1s² ,2s² ,2p⁶ ,3s² ,3p⁶ ,4s² ,3d¹⁰,4p⁵ . 

P-4th,        G-17th

The exact position of electron cannot be determined therefore concept of orbits was replaced by the concept of probability.

Violet colour is scattered the most and red the least as the intensity of scattered light is found to be inversely proportional to the fourth power of wavelength of light.

X-rays and ultraviolet rays are electromagnetic waves of frequency greater than that of violet light.

Uses:

X-rays are used for studying atomic arrangement in crystals.

Ultraviolet rays are used for detecting the purity of gems, eggs, ghee etc.

4000 Å to 8000 Å .

Blue colour

Hint: When light of certain frequency falls on that atom or molecule, this atom or molecule responds to the light, whenever the size of the atom or molecule comparable to the wavelength of light. The sizes of nitrogen and oxygen molecules in atmosphere are comparable to the wavelength of blue light. These molecules act as scattering centers for scattering of blue light. This is also the reason that we see the sky as blue.

The clouds are nearer the earth surface and they contain dust particles and aggregates of water molecules of sizes bigger than the wavelength of visible light. Therefore, the dust particles and water molecules present in clouds scatter all colours of incident white light from sun to the same extent and hence when the scattered light reaches our eye, the clouds are seen white.

Correct option is C) Carbon

(a) Gamma rays-wavelength shorter than 0.1 Å

(b) X-rays-wavelength range 0.1 Å to 100 Å

(c) Ultraviolet rays-wavelength range 100 Å to 4000 Å

(d) Visible light-wavelength range 4000 Å to 8000 Å

(e) Infrared radiations-wavelength range 8000 Å to 107 Å

(f) Microwaves-wavelength range 107 Å to 1011 Å

(g) Radio waves-wavelength above 1011Å

(i)Gamma rays are of highest frequency.

(ii)Infrared rays are used for taking photographs in dark.

(iii)Gamma rays are produced by the changes in the nucleus of an atom.

(iv)X-Rays are of wavelength nearly 0.1 nm.

(a) Gamma rays, X-rays, infrared rays, micro waves, radio waves.

(b) Microwave is used for satellite communication.

When white light from sun enters the earth's atmosphere, the light gets scattered i.e., the light spreads in all directions by the dust particles, free water molecules and the molecules of the gases present in the atmosphere. This phenomenon is called scattering of light.

(a) A- Gamma rays, B-infrared radiations

(b) Ratio of speeds of these waves in vacuum is 1:1 as all electromagnetic waves travel with the speed of light in vacuum.

(a) Gamma ray.

(b) Gamma rays have strong penetrating power.

(a) X-rays are used in the study of crystals.

(b) It is also used to detect fracture in bones.

(i) For blue light, approximate wavelength=4800 Å

(ii) For red light, approximate wavelength=8000 Å