Ray Optics and Optical Instruments — Physics STD 12 Science — Question

Identify the correct statement from the following.

In summer, a mild wind is often found on the shore of a calm river. This is caused due to,

1. Difference in thermal conductivity of water and soil.
2. Convection currents.
3. Conduction between air and the soil.
4. Radiation from the soil.

What is immaterial for an electric fuse wire(a) Its specific resistance(b) Its radius(c) Its length(d) Current flowing through it

Two balls are thrown simultaneously in air. The acceleration of the centre of mass of the two balls while in air:

Photoelectric emmision occurs only when the incident light has more than a certain minimum?

Which of the following statements about the Bohr model of the hydrogen atom is false(a) Acceleration of electron in n = 2 orbit is less than that in n = 1 orbit(b) Angular momentum of electron in n = 2 orbit is more than that in n = 1 orbit(c) Kinetic energy of electron in n = 2 orbit is less than that in n = 1 orbit(d) Potential energy of electron in n = 2 orbit is less than that in n = 1 orbit

Which of the following is quantised according to Bohr’s theory of hydrogen atom(a) Linear momentum of electron(b) Angular momentum of electron(c) Linear velocity of electron(d) Angular velocity of electron

Which of the relations is correct for radioactive atom ?

Which one of the following is feebly repelled by a magnet?

If the length of potentiometer wire is increased, then the length of the previously obtained balance point will(a) Increase(b) Decrease(c) Remain unchanged(d) Become two times