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Why are infra-red waves often called heat waves? Explain.
Infrared waves produced from hot bodies. Hence, it often called heat waves.
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What do you understand by the statement, 'Electromagnetic waves transport momentum'?
When electromagnetic waves hit the body the mass is lost by the momentum is conserved. i.e., transferred from Electromagnetic waves to the body.
If light of wavelength 412.5 nm is incident on each of the metals given below, which ones will show photoelectric emission and why?
| Metal | Work Function (eV) |
| Na | 1.92 |
| K | 2.15 |
| Ca | 3.20 |
| Mo | 4.17 |
A metal will show photoelectric emission in below situation:
E ≥ work function
Now according to the relation below:
The work function of k and Na are less than the incident energy of the photon. Hence, only potassium (k) and Sodium (Na) will show photoelectric emission.
The surface of a metal is illuminated with the light of 400 nm. The kinetic energy of the ejected photoelectrons was found to be 1.68 eV. The work function of the metal is (hc = 1240 eV nm)
3.09 eV
1.41 eV
151 eV
1.68 eV
B.
1.41 eV
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Mock Test Series
