Explore topic-wise InterviewSolutions in .

(a) move with the same speed

(c) move with the same kinetic energy

(d) have fallen through the same height.

Frequency should be greater than threshold frequency of photosensitive material.

hv = \(\frac{1}{2} m v_{\max }^{2}\) + ϕ
Where, hv = energy of incident light
ϕ = Work function
\(\frac{1}{2} m v_{\max }^{2}\) = Maximum kinetic energy of emitted photelectrons.

Wave theory of light is confirmed by Davisson and Germer experiment.

The minimum amount of energy is required by an electron to just eject from the metal surface is called work function of the metal.

(b) ∞
From Heisenberg Uncertainty principle
Δp_xΔx > \(\frac{h}{2 \pi}\)
For accuracy in position change Δx = 0
∴ Δp_x = \(\frac{h}{2 \pi \times 0}\) = ∞

Davisson-Germer experiment was to study the wave properties of electrons.

(d) Diffraction
Diffraction property is shown by Davisson and Germer.

λ = \(\frac{h}{p}\)
Where, h = Planck’s constant
p = momentum.

(d) Violet, blue, sky blue
Work function ϕ = hv₀ = \(\frac{h c}{\lambda_{0}}\)
⇒ ϕ ∝ \(\frac{1}{\lambda_{0}}\)
They will be emitted at low wavelength

(a) 2.5 eV
From Einstein photoelectric equation
hv = ϕ + E_K
40 eV = ϕ + 37.5 eV
ϕ = (40 – 37.5) eV
= 2.5 eV

For a perfectly reflecting solid sphere of radius ‘r’ kept in the path of a parallel beam of light of large aperture with intensity ‘I’, force exerted =πr²l/C

λ  = 663 x 10^–9 m,  θ= 60°, n = 1 x 10¹⁹, λ = h/p

=> P = p/λ = 10^–27

Force exerted on the wall = n(mv cosθ –(–mv cosθ)) = 2n mv cos θ.

= 2 x 1 x 10¹⁹ x 10^–27 x ½ = 1 x 10^–8 N.

λ₁ = 500 nm = 500 x 10^–9m, λ₂ = 700 nm = 700 x 10^–9 m

E₁ – E₂ = Energy absorbed by the atom in the process. = hc [1/λ₁ – 1/λ₂]

=> 6.63 x 3[1/5 – 1/7] x 10^–19 = 1.136 x 10^–19 J

(c) The electron and the proton respectively (c) λ_e > λ_p.

(a) there is a minimum frequency below which no photoelectrons are emitted 

(b) the maximum kinetic energy of photoelectrons depends only on the frequency of light and not on its intensity 

(c) even when the metal surface is faintly illuminated the photoelectrons leave the surface immediately

(a) The photoelectric effect will take place only if  v > v_0.

(d) It may come out with a kinetic energy less than hv - ϕ.

(b) the photoelectrons are emitted but are reabsorbed by the emitter metal

Curve d represent the saturation photocurrent.

(a) the number of photons emitted by the source in unit time increases
(b) the total energy of the photons emitted per unit time increases