Advertisements
Advertisements
प्रश्न
The work function of a metal is 2.31 eV. Photoelectric emission occurs when the light of frequency 6.4 × 1014 Hz is incident on the metal surface. Calculate
- the energy of the incident radiation,
- the maximum kinetic energy of the emitted electron and
- the stopping potential of the surface.
उत्तर
(i) Frequency of incident radiation = ν = 6.4 × 1014 Hz
Energy of incident radiation = E = hν = 6.6 × 10−34 × 6.4 × 1014 = 42.24 × 10−20 J
(ii) KEmax = hν − Φ0
∴ KEmax = 42.24 × 10−20 − 2.31 × 1.6 × 10−19 = 5.28 × 10−20 J
(iii) If stopping potential = VS, then
eVS = KEmax
∴ VS = `"KE"_"max"/"e"`
= `(5.28 xx 10^-20)/(1.6 xx 10^-19)`
= 3.3 × 10−1
= 0.33 V
APPEARS IN
संबंधित प्रश्न
The work function of caesium metal is 2.14 eV. When light of frequency 6 × 1014 Hz is incident on the metal surface, photoemission of electrons occurs. What is the
(a) maximum kinetic energy of the emitted electrons,
(b) Stopping potential, and
(c) maximum speed of the emitted photoelectrons?
Quarks inside protons and neutrons are thought to carry fractional charges [(+2/3)e; (–1/3)e]. Why do they not show up in Millikan’s oil-drop experiment?
How does one explain the emission of electrons from a photosensitive surface with the help of Einstein's photoelectric equation?
How will the thermionic current vary if the filament current is increased?
An isolated metal sphere is heated to a high temperature. Will it become positively charged due to thermionic emission?
The constant A in the Richardson−Dushman equation for tungsten is 60 × 104 A m−2K−2. The work function of tungsten is 4.5 eV. A tungsten cathode with a surface area 2.0 × 10−5 m2 is heated by a 24 W electric heater. In steady state, the heat radiated by the heater and the cathode equals the energy input by the heater and the temperature becomes constant. Assuming that the cathode radiates like a blackbody, calculate the saturation current due to thermions. Take Stefan's Constant = 6 × 10−8 W m−2 K−1. Assume that the thermions take only a small fraction of the heat supplied.
Answer the following question.
Define the term "Threshold frequency", in the context of photoelectric emission.
The wavelength λe of an electron and λp of a photon of same energy E are related by
Photoelectric emission is observed from a metallic surface for frequencies ν1 and ν2 of the incident light (ν1 > ν2). If the maximum value of kinetic energy of the photoelectrons emitted in the two cases are in the ration 1 : n then the threshold frequency of the metallic surface is ______.
Give an example each of a metal from which photoelectric emission takes place when irradiated by
- UV light
- visible light.
