Two bodies, A and B of equal mass are kept at heights 20 m and 30 m respectively. Calculate the ratio of their potential energies. 

How can the work done be measured when force is applied at an angle to the direction of displacement? 

What is the main energy transformation that occurs in:

1. Photosynthesis in green leaves;

Which class of levers has a mechanical advantage always greater than one? What change can be brought about in this lever to increase its mechanical advantage? 

Write an expression to show the relationship between mechanical advantage, velocity ratio and efficiency for a simple machine? 

State Snell’s Law of Refraction of light. 

Mention one difference between reflection of light from a plane mirror and total internal reflection of light from a prism. 

The diagram given alongside shows a right-angled prism with a ray of light incident on the side AB (The critical angle for glass is 42^o)

i) copy the diagram and complete the path of the ray of light in and out of the glass prism.

An object is placed in front of a converging lens at a distance greater than twice the focal length of the lens. Draw a ray diagram to show the formation of the image? 

Why are infra-red radiations preferred over ordinary visible light for taking photographs in the fog?