Shimmering effect around a camp fire is due to

1. reflection of light
2. dispersion of light
3. scattering of light
4. refraction of light

In the sound wave produced by a vibrating tuning fork shown below, the half wavelength is given by:

1. PQ
2. QR
3. QS
4. PT

The number of beta particles emitted by radioactive substance is twice the number of alpha particles emitted by it. The resulting daughter nuclei is as

1. isobar of parent
2. isomer of parent
3. isotone of parent
4. isotope of parent

Which of the following forces cannot create a moment of force?

1. Action-reaction forces
2. Gravitational forces
3. Electric forces
4. Frictional forces