Solution

f=qB/2πm
f ∝ 1/m
Mass of an electron is less than that of proton, therefore, its frequency of revolution will be higher than that of proton.

Solution

(a) Water purification : Ultraviolet radiation.
(b) Eye surgery : Ultraviolet radiation/laser

Solution

Solution

When lighter nuclei combine to form a heavier nucleus, the binding energy per nucleon increases and energy is released. Therefore, the daughter nucleus would have higher binding energy per nucleon.

Solution

Skywave propagation

Solution

Let resistances of bulbs P and Q be R and 2R respectively. As they are connected in series, so current through each bulb is same. Let the current be I.
P₁/P₂=I²R₁/I²R₂=R₁/R₂=1/2
P₁:P₂=1:2

Solution

Solution

(a) Infra-red waves are called heat waves because they raise the temperature of the object on which they fall and hence increase their thermal motion. They also affect the photographic plate and are readily absorbed by most of the materials.
(b) Electromagnetic waves transport momentum. This means that when an electromagnetic wave travels through space with energy U and speed c, then it transports linear momentum p = U/C. If a surface absorbs the waves completely, then momentum ‘p’ is delivered to the surface. If the surface reflects the wave, then momentum delivered by both incident and reflected wave adds on to give ‘2p’ momentum.

Solution

The energy of incident radiation is greater than the work function of sodium and potassium, but less than that of calcium and molybdenum. Therefore, photoelectric emission will take place in sodium and potassium.

Solution