Q.1. The kinetic energy of photoelectrons emitted by a photosensitive surface depends on the intensity of the incident radiation. (1981- 2 Marks)
Solution. For photoelectric effect
hv – hv0 = (K.E.)max
where h = Planck’s constt.
v0 = Threshold frequency
⇒ (K.E.)max ∝ n
K.E. does not depend on the intensity of incident radiation.
Q.2. In a photoelectric emission process the maximum energy of the photo-electrons increases with increasing intensity of the incident light. (1986 - 3 Marks)
Solution. (K.E.)max = hv – hv0 ⇒ (K.E.)max ∝ v
Thus maximum kinetic energy is proportional to frequency and not intensity.
Q.3. For a diode the variation of its anode current Ia with the anode voltage Va at two different cathode temperatures T1 and T2 is shown in the figure. The temperature T2 is greater than T1. (1986 - 3 Marks)
Solution. Note : When the cathode temperature is higher, then more number of electrons will be emitted which in turn will increase the anode current.
Q.4. The order of magnitude of the density of nuclear matter is 104 kg m–2. (1989 - 2 Marks)
where A = mass number.
Note : The order of nuclear density is 1017 kg/m3.