Advertisements
Advertisements
प्रश्न
Consider Figure for photoemission.
How would you reconcile with momentum conservation? Note light (photons) have momentum in a different direction than the emitted electrons.
Advertisements
उत्तर
The momentum is transferred to the metal. At the microscopic level, atoms absorb the photon and its momentum is transferred mainly to the nucleus and electrons. The excited electron is emitted. Conservation of momentum needs to be accounted for the momentum transferred to the nucleus and electrons.
APPEARS IN
संबंधित प्रश्न
Find the (a) maximum frequency and (b) minimum wavelength of X-rays produced by 30 kV electrons.
Why should gases be insulators at ordinary pressures and start conducting at very low pressures?
The work function of the following metals is given : Na 2.75 ev, K = 2.3 eV, Mo = 4.17 eV and Ni = 5.15 eV. Which of these metals will not cause photoelectric emission for radiation of wavelength 3300 Å from a laser source placed 1 m away from these metals? What happens if the laser source is brought nearer and placed 50 cm away?
How will the thermionic current vary if the filament current is increased?
Would you prefer a material with a high melting point or a low melting point to be used as a cathode in a diode?
Would you prefer a material with a high work-function or a low work-function to be used as a cathode in a diode?
An isolated metal sphere is heated to a high temperature. Will it become positively charged due to thermionic emission?
A diode value is connected to a battery and a load resistance. The filament is heated, so that a constant current is obtained in the circuit. As the cathode continuously emits electrons, does it become more and more positively charged?
Why does thermionic emission not take place in non-conductors?
Let i0 be the thermionic current from a metal surface when the absolute temperature of the surface is T0. The temperature is slowly increased and the thermionic current is measured as a function of temperature. Which of the following plots may represent the variation in (i/i0) against (T/T0)?
The anode of a thermionic diode is connected to the negative terminal of a battery and the cathode to its positive terminal.
Answer the following question.
Define the term "Threshold frequency", in the context of photoelectric emission.
The wave associated with a moving particle of mass 3 × 10–6 g has the same wavelength as an electron moving with a velocity 6 × 106 ms–1. The velocity of the particle is
Emission of electrons by the absorption of heat energy is called ____________ emission.
What do you mean by electron emission? Explain briefly various methods of electron emission.
In which case is electron emission from a metal not known?
Name the factors on which photoelectric emission from a surface depends.
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.
