Advertisements
Advertisements
प्रश्न
Give the construction and working of photo emissive cell.
Advertisements
उत्तर
Photo emissive cell: Its working depends on the electron emission from a metal cathode due to irradiation of light or other radiations.
Construction:
1. It consists of an evacuated glass or quartz bulb in which two metallic electrodes – that is, a cathode and an anode are fixed.
2. The cathode C is semi-cylindrical in shape and is coated with a photo sensitive material. The anode A is a thin rod or wire kept along the axis of the semi-cylindrical cathode.
3. A potential difference is applied between the anode and the cathode through a galvanometer G.
Construction of photo cell
Working:
When the cathode is irradiated with suitable radiation, electrons are emitted from it. These electrons are attracted by the anode and hence a current is produced which is measured by the galvanometer.
For a given cathode, the magnitude of the current depends on
- the intensity to incident radiation and
- the potential difference between anode and cathode.
APPEARS IN
संबंधित प्रश्न
When a metallic surface is illuminated with radiation of wavelength λ, the stopping potential is V. If the same surface is illuminated with radiation of wavelength 2λ, the stopping potential is `"V"/4`. The threshold wavelength for the metallic surface is
A light source of wavelength 520 nm emits 1.04 × 1015 photons per second while the second source of 460 nm produces 1.38 × 1015 photons per second. Then the ratio of power of second source to that of first source is
If the mean wavelength of light from sun is taken as 550 nm and its mean power as 3.8 × 1026 W, then the average number of photons received by the human eye per second from sunlight is of the order of
Photons of wavelength λ are incident on a metal. The most energetic electrons ejected from the metal are bent into a circular arc of radius R by a perpendicular magnetic field having magnitude B. The work function of the metal is
The work functions for metals A, B and C are 1.92 eV, 2.0 eV and 5.0 eV respectively. The metal/metals which will emit photoelectrons for a radiation of wavelength 4100Å is/are
What is the photoelectric effect?
What is a surface barrier?
How many photons of frequency 1014 Hz will make up 19.86 J of energy?
When a light of frequency 9 × 1014 Hz is incident on a metal surface, photoelectrons are emitted with a maximum speed of 8 × 105 ms−1. Determine the threshold frequency of the surface.
When a 6000 Å light falls on the cathode of a photo cell, photoemission takes place. If a potential of 0.8 V is required to stop emission of electron, then determine the
- frequency of the light
- energy of the incident photon
- work function of the cathode material
- threshold frequency and
- net energy of the electron after it leaves the surface.
