Advertisements
Advertisements
प्रश्न
Find the (a) maximum frequency, and (b) minimum wavelength of X-rays produced by 30 kV electrons.
उत्तर
Potential of the electrons, V = 30 kV = 3 × 104 V
Hence, energy of the electrons, E = 3 × 104 eV
Where,
e = Charge on an electron = 1.6 × 10−19 C
(a) Maximum frequency produced by the X-rays = v
The energy of the electrons is given by the relation:
E = hv
Where,
h = Planck’s constant = 6.626 × 10−34 Js
∴ v = `"E"/"h"`
= `(1.6 xx 10^(-19) xx 3 xx 10^4)/(6.626 xx 10^(-34))`
= 7.24 × 1018 Hz
Hence, the maximum frequency of X-rays produced is 7.24 × 1018 Hz.
(b) The minimum wavelength produced by the X-rays is given as:
`lambda = "c"/"v"`
= `(3xx10^8)/(7.24 xx 10^18)`
= 4.14 × 10−11 m
= 0.0414 nm
Hence, the minimum wavelength of X-rays produced is 0.0414 nm.
APPEARS IN
संबंधित प्रश्न
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?
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?
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?
The cathode of a diode valve is replaced by another cathode of double the surface area. Keeping the voltage and temperature conditions the same, will the place current decrease, increase or remain the same?
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 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 work function of aluminum is 4⋅2 eV. If two photons each of energy 2⋅5 eV are incident on its surface, will the emission of electrons take place? Justify your answer.
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
Why do metals have a large number of free electrons?
Define the work function of a metal. Give its unit.
What do you mean by electron emission? Explain briefly various methods of electron emission.
A 150 W lamp emits light of the mean wavelength of 5500 Å. If the efficiency is 12%, find out the number of photons emitted by the lamp in one second.
In which case is electron emission from a metal not known?
