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The correct option is (A).

Rayleigh scattering is the (dominantly) elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the radiation. The amount of scattering is inversely proportional to the fourth power of the wavelength.

(i) Microwaves are high energy electromagnetic waves. It is believe that they agitate the molecules to move faster and faster. It destroys vitamins, minerals and protein. It changes them into products which may cause cancer, memory loss and decrease in intelligence.However, it is believed that a limited use has no harmful effects. In a modern fast life, it saves a lot of time and is a clean method of warming the food. 

(ii) It is believed that microwaves or radio waves of cellophane could interact with our heart. This problem is more serious for people using cardiac pace makers. Hence it is advised not to keep cell phone in breast pocket. 

(iii) X-ray is a type of high energy radiation. This can be destructive to all living cells and can cause DNA damage and mutation. They have bad effects on pregnancy and child birth. They can deform the body of infant and could be fatal to his life. They can harm the tissues of the bones called ―bone marrow‘‘ .Thus, there can be congenital disorders (birth defects). 

(iv) Ultrasound waves are high frequency sound waves. They are used to treat pain conditions and promote tissue healing in physiotherapy. The ultrasound machine is also used in the medical field to follow the growth of baby in the womb of the pregnant women. However, it is being misused to know the sex of the unborn baby.

The process of separation of light into its component colours while passing through a medium is called dispersion of light. The band of coloured components of a light beam is called spectrum.

The different colours of light in the spectrum of white light are violet, indigo, blue, green, yellow, orange and red.

Correct option is  C) Visible rays

Our eyes are sensitive to light (electromagnetic radiation). Its wavelength range is 400 nm to 700 nm.

[Note: Wavelength (λ) goes on decreasing and frequency (ν) goes on increasing from red (λ ≃ 700 nm) → orange → yellow → green → blue → indigo → violet (A ≃ 400 nm). c = vλ, where c is the speed of light in vacuum.]

• The critical angle of diamonds is very low, i.e., 24.4°. 
• So if a light ray enters diamond, it undergoes total internal reflection. 
• It makes the diamond shine brilliant. 
• So total internal reflection is main cause of brilliance of diamonds.
• Majority of people are attracted towards diamonds due to this property. 
• So we have to thoroughly appreciate total internal reflection for brilliance of diamonds.

The light ray undergoes refraction.

B) diverging lens

Yes. The speed of light changes when it travels from one medium to another medium. So the light may bend towards normal or away from normal.

• Ray diagrams are very useful in optics. 
• By the ray diagrams, we can easily find the values of image distance, object distance, focal length, radius of curvature, magnification, etc. 
• These results are exactly equal to the result gotten by an experiment. 
• For example : In the experiment, with a convex lens, we get clear image of an object, on a screen by adjusting the screen.

Then, we measure the image distance (v) practically. This takes more time and requires equipped lab also. 

But, by simply draw a ray diagram on a paper, we can get exact image distance (v) very easily, without lab. 

• So, ray diagrams are very useful in the construction of microscopes, telescopes, etc. 
• Hence, one can trust and depend on the result of ray diagrams instead of several lab experiments. 
• So, I appreciate the ray diagrams.

The refraction of curved surfaces are used in various aspects such as 

1. In microscope to enlarge microscopic objects. 

2. In telescopes to see celestial objects.

3. To correct eye defects like myopia, hypermetropia and presbyopia.

So refraction at curved surfaces is thoroughly appreciated.

The rays which move very close to the principal axis which can be treated as parallel are called paraxial rays.

It will act as a concave lens.

Yes. A convergent lens is placed in a higher refractive index of medium the nature of the lens changes i.e., it acts as divergent lens.

Yes. A lens is placed in a medium of a high refractive index than that of the lens then nature of lens changes (M_L > M_g).

Given that the lens is forming an image which is always erect and diminished. So it is virtual also. Such type of image is formed by concave lens.

Concave lens.

D) between focal point and optic centre

Chromium is electroplated on car parts such as bumpers and bicycle handlebars made of steel.

D) at any position

When an object is placed at a very large distance from a diverging lens, then image is formed at the focus of the lens. Therefore, the focal length of the lens is 20 cm.

1. Chromium is electroplated on other metals. 

2. Gold is electroplated on other cheap metals.

Because the free ends of a conductivity tester are dipped into a conducting solution then, it behaves like a current carrying wire and a current carrying wire behaves as a magnet because it produces magnetic field around it. And, due to this there is deflection in the compass.

Tin is electroplated on iron for making ‘cans’ used for storing food.

Tin is less reactive than iron. Tin coating prevents food from coming in contact with iron and thus prevents it from getting spoiled.

Electric current produces magnetic effect which causes deflection of the magnetic needle of a compass. So, when the free ends of a tester are dipped into a solution which is a good conductor of electricity, the needle shows deflection.

The list of five objects around you which are electroplated is: 

1. Kitchen utensils. 

2. Jewelry 

3. Car parts 

4. Cans 

5. Taps

Diagram A shows the correct observation.

Heating effect of electric current.

No, Yes, No, Yes

Here, r = 80 cm = 0.80 m,

u = 14 rev/25 s

As centripetal acceleration = 4π²v²r

= 4 x (3.14) 2 x (14/25)² x 0.80 = 9.9 ms^-2

At every point the acceleration is along the radius and towards the centre.

(d) sugar solution in diluted water

There could be several possible reasons for not glowing of the bulb: 

(a). The bulb may be fused. 

(b). Even after replacing the bulb if it does not glow, then the connection may be loose or faulty. 

(c). Even after checking and repairing the connections if the bulb does not glow that means the solution does not conduct electricity.

Yes, air is a poor conductor of electricity. No, under certain conditions, such as during lightning, air may conduct electricity.

(i) It indicates the presence of current in the circuit. 

(ii) The bulb did not glow because the current was not sufficient to make it glow. 

(iii) Deflection in the magnetic compass will increase. 

(iv) Deflection in the compass will increase further.

If the water is distilled water and lemon juice is not added, no current will pass through the circuit. If the water taken is salty, then a feeble current will pass through the circuit and bubbles will be seen on the negative electrode.

Electroplating is a costly process and the corrosion-resistant metal like
Chromium is also very costly.

Yes, copper from the copper sulphate solution will be deposited on the carbon rod. Copper from the copper plate will be dissolved into the copper sulphate solution for electroplating.

The object to be electroplated is connected to the negative terminal of battery. The electrolyte is acidified copper sulphate. The free copper in the solution gets deposited to the iron object. An equal amount of copper gets dissolved in the solution from the other electrode.

In the process of electroplating, the metal to be electroplated is taken as cathode and the one used for coating is chosen as the anode. And, we know, anode is positive terminal and the cathode is negative terminal. Thus, negative terminal will be connected to the iron object.

Output voltage = 220 ± 1% 

1% of 220V = 2.2v

The resistance of bulb R = V²/P = (220)²/100 = 484Ω

(a) For minimum power consumed V₁ = 220 – 1% = 220 – 2.2 = 217.8

∴ i = V₁/R = 217.8/484 = 0.45A

Power consumed = i × V₁ = 0.45 × 217.8 = 98.01W

(b) for maximum power consumed V₂ = 220 + 1% = 220 + 2.2 = 222.2

∴ i = V₂/R = 222.2/484 = 0.459

Power consumed = i × V₂ = 0.459 × 222.2 = 102W

(a) The power consumed by a coil of resistance R when connected across a supply v is P = v²/R

The resistance of the heater coil is, therefore R = V²/P = (250)²/500 = 125Ω

(b) If P = 1000 w then R = V²/P = (250)²/1000 = 62.5Ω

P = 1000

V = 220v

R = V²/P = 48400/1000 = 48.4Ω

Mass of water = 1/100 x 1000 = 10kg

Heat required to raise the temp. of given amount of water = msΔt = 10 × 4200 × 25 = 1050000

Now heat liberated is only 60%. So V²/R x T x 60% = 1050000

=> (220)²/48.4 x 60/100 x T = 1050000 => T = 10500/6 x 1/60nub = 29.16min

3/21 = 8/56 = 7/49

3/27 = 6/54 = 9/81

and so on

Correct option is (b) 14

1. Barter System 

2. Money transaction

Monetary policy is the policy used to control inflation. 

Its three instruments are

1. Open market operation: The RBI sells and buys government securities in the open market. This is known as open market operation. At the time of high inflation, RBI sells government securities to the public. The money from the economy ow to the RBI. Since the money in the economy falls the demand for goods and services too will fall and the price will come down. So the inflation is controlled. 

2. Changes in the bank rate: When inflation is high RBI will raise the bank rate. At higher bank rate people will demand less loans, they will save more. This will lead to a reduction in the demand, the price level too will fall. An increased bank rate also will lead to a fall in the money supply. 

3. Varying the reserve requirement: At the time of high inflation, the RBI can make necessary changes in the various reserve requirements like CRR, CDR, SLR etc. At the time of inflation RBI raises the CRR, that means more money has to be kept in the RBI. This will reduce the money supply in the economy. So the demand will come down and the general price level too.

By double coincidence of wants, we mean the need to have mutually exchangeable goods and the compulsion for exchange. This system is associated with the barter system.

• Fiat money: Money with no intrinsic value Eg. Currency notes, coins. 
• Full-bodied money: Money whose face value is equal to the intrinsic value Eg. Gold coins, silver coins. 
• Legal tender money: Money issued by the monetary authority or the government which cannot be refused by anyone. Eg. Currency notes.