Advertisements
Advertisements
Question
Define the term "Intensity" in the photon picture of electromagnetic radiation.
Advertisements
Solution
The intensity I is defined as the total amount of energy falling on a given surface/Region per unit time 'rand per unit area A:
If the total energy emitted = nhv
Then, I = `(nhν)/(At)`
APPEARS IN
RELATED QUESTIONS
Given below are some famous numbers associated with electromagnetic radiations in different contexts in physics. State the part of the electromagnetic spectrum to which each belongs.
(a) 21 cm (wavelength emitted by atomic hydrogen in interstellar space).
(b) 1057 MHz (frequency of radiation arising from two close energy levels in hydrogen; known as Lamb shift).
(c) 2.7 K [temperature associated with the isotropic radiation filling all space-thought to be a relic of the ‘big-bang’ origin of the universe].
(d) 5890 Å - 5896 Å [double lines of sodium]
(e) 14.4 keV [energy of a particular transition in 57Fe nucleus associated with a famous high resolution spectroscopic method (Mössbauer spectroscopy)].
What is the range of the wavelength of the following electromagnetic waves?
(a) Gamma rays.
Name the waves of wavelength nearly 0.1 nm.
Moseley's Law for characteristic X-ray is √v = a(Z − b). Here,
For a given material, the energy and wavelength of characteristic X-rays satisfy
(a) E(Kα) > E(Kβ) > E(Kγ)
(b) E(Mα) > E(Lα) > E(Kα)
(c) λ(Kα) > λ(Kβ) > λ(Kγ)
(d) λ(Mα) > λ(Lα) > λ(Kα).
Iron emits Kα X-ray of energy 6.4 keV. Calculate the times taken by an iron Kα photon to cross through a distance of 3 km.
(Use Planck constant h = 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
State the name and the range of wavelength of the invisible electromagnetic waves beyond the red end of the visible spectrum.
Name the part of the electromagnetic spectrum which is:
Suitable for radar systems used in aircraft navigation.
An e.m. wave exerts pressure on the surface on which it is incident. Justify.
Light of wavelength `3500A` is incident on two metals A and B whose work functions are 3.2 eV and 1.9 eV respectively. Which metal will emit photoelectrons?
