Advertisements
Advertisements
प्रश्न
Threshold frequency, ν0 is the minimum frequency which a photon must possess to eject an electron from a metal. It is different for different metals. When a photon of frequency 1.0 × 1015 s–1 was allowed to hit a metal surface, an electron having 1.988 × 10–19 J of kinetic energy was emitted. Calculate the threshold frequency of this metal. Show that an electron will not be emitted if a photon with a wavelength equal to 600 nm hits the metal surface.
उत्तर
For the emission of electrons from metal the frequency of the striking light should be higher than that of its threshold frequency.
We have `hv = hv_0 + K.E`
`v_0 = (v - K.E)/h` ......(1)
Given, `v = 10^15 s^-1`, K.E = `1.988 xx 10^-19` J
Thus (1) gives
`v_0 = 7 xx 10^14 s^-1`
Given, `lambda` = 600 nm
`v = c/lambda = 5 xx 10^14 s^-1`
As `v_0 > v`, thus the electrons do not emit.
APPEARS IN
संबंधित प्रश्न
Arrange the following type of radiations in increasing order of frequency:
- radiation from microwave oven
- amber light from traffic signal
- radiation from FM radio
- cosmic rays from outer space and
- X-rays.
Nitrogen laser produces radiation at a wavelength of 337.1 nm. If the number of photons emitted is 5.6 × 1024, calculate the power of this laser.
Assertion (A): Black body is an ideal body that emits and absorbs radiations of all frequencies.
Reason (R): The frequency of radiation emitted by a body goes from a lower frequency to higher frequency with an increase in temperature.
The energy ratio of a photon of wavelength 3000 Å and 6000 Å is ______.
A particular station of All India Radio, New Delhi, broadcasts on a frequency of 1,368 kHz (kilohertz). The wavelength of the electromagnetic radiation emitted by the transmitter is ______
[speed of light, c = 3.0 × 108 ms−1]
A particular station of All India Radio, New Delhi, broadcasts on a frequency of 1,368 kHz (kilohertz). The wavelength of the electromagnetic radiation emitted by the transmitter is ______.
[speed of light, c = 3.0 × 108 ms−1]
When a certain metal was irradiated with light of frequency 3.2 × 1016 Hz, the photoelectrons emitted had twice the kinetic energy as did photoelectrons emitted when the same metal was irradiated with light of frequency 2.0 × 1016 Hz. The light of frequency v0 for the metal is ______ × 1015 Hz.
The wavelength associated with an electron equal to the wavelength of a proton would be ______ × 103.
(mass of e = 9 × 10−28 g; mass of proton = 1.6725 × 10−24 g)
What is the work function of the metal if the light of wavelength 4000 Å generates photoelectrons of velocity 6 × 105 ms−1 from it?
(Mass of electron = 9 × 10−31 kg
Velocity of light = 3 × 108 ms−1
Planck's constant = 6.626 × 10−34 Js
Charge of electron = 1.6 × 10−19 JeV−1)
The region in the electromagnetic spectrum where the Balmer series lines appear is ______.
