Advertisements
Advertisements
प्रश्न
A photocell is used to automatically switch on the street lights in the evening when the sunlight is low in intensity. Thus it has to work with visible light. The material of the cathode of the photocell is ______.
पर्याय
Zinc
Aluminum
Nickel
Potassium
Advertisements
उत्तर
A photocell is used to automatically switch on the street lights in the evening when the sunlight is low in intensity. Thus it has to work with visible light. The material of the cathode of the photocell is potassium.
Explanation:
The photocell is a resistor or sensor which changes its resistance depending on the amount of light it receives.
- Photocells consist of cathodes and anodes where the cathode is photosensitive which emits electrons when light falls on it and the anode collects the electrons emitted by the cathode.
- The element that is used as a cathode should have less ionization energy so that it can emit an electron when subjected to light.
- Potassium has lower ionization energy. Hence it is used in photocells as the cathode.
संबंधित प्रश्न
If NRed and NBlue are the numbers of photons emitted by the respective sources of equal power and equal dimensions in unit time, then ______.
Choose the correct option.
The equation E = pc is valid ______.
Ultraviolet radiation of 6.2 eV falls on an aluminum surface (work function 4.2 eV). The kinetic energy in joules of the fastest electron emitted is ______
Define threshold frequency.
What is cut-off or stopping potential?
What is mean by the dual nature of matter?
Calculate the stopping potential when the metal with the work function 0.6 eV is illuminated with the light of 2 eV.
In what year did Hertz perform experiments on the generation and detection of electromagnetic waves?
Which experiments led to important discoveries in atomic structure?
Where did a fluorescent glow appear during electric discharge through low-pressure gas?
What determined the colour of the fluorescent glow, and what colour was observed for soda glass?
Who discovered cathode rays in 1870?
What did Crookes suggest in 1879 about cathode rays?
What value is given for the speed of light?
How did the value of \[e/m\] depend on the gas introduced in the discharge tube?
What did the independence of \[e/m\] from cathode material and gas suggest?
What happened when certain metals were irradiated with ultraviolet light, as found in 1887?
Who named these particles electrons in 1897?
What value was measured for the elementary charge?
What did Millikan’s oil-drop experiment establish?
Which measured values could be used to determine the mass \[m\] of the electron?
