The phenomenon of formation of three-dimensional image by the interference of two light beams from laser or other coherent sources of light is called :

Consider the following statements :

1. Atom bomb is based upon the principle of uncontrolled nuclear fusion

2. Hydrogen bomb is based upon the principle of uncontrolled nuclear fission

3. Nuclear reactor is based upon the principle of controlled nuclear fission

Which of the statements given above is/are correct?

Which of the following waves can propagate in a vacuum ?

1. Radio waves

2. Light waves

3. X-rays

4. Ultrasonic waves

Select the correct answer using the codes given below :

Paper becomes brittle and yellow with age. Why?

1. The acid content in paper causes brittleness to develop

2. In the presence of visible light, photosensitised oxidation occurs

3. The ultra-violet component of sunlight causes photolysis of cellulose by direct cleavage of the cellulose polymer

Water kept in an old ‘surahi’ is less cold than the water in a new one. Why?

The best conductor of electricity is :

Which of the following is the correct sequence of the regions of the sun as one moves from its core to the surface?

1. Photosphere 

2. Chromosphere

3. Convection zone 

4. Corona

You are standing in a lift. The force on the floor of the lift due to your weight will :

If the earth were 3 times as far from the sum as it is now, how would the gravitaltional attraction compare with its present value?

Two cars, passing each other at high speed, are in danger of side swiping because :