Advertisements
Advertisements
Question
The ratio of contributions made by the electric field and magnetic field components to the intensity of an EM wave is ______.
Options
`c : 1`
`c^2 : 1`
`1 : 1`
`sqrt(c) : 1`
Advertisements
Solution
The ratio of contributions made by the electric field and magnetic field components to the intensity of an EM wave is 1 : 1.
Explanation:
Average energy by electric field E0 is Uav
`U_(av) = 1/2 ε_0 E_0^2`
But E0 = cB0
(Uav) electric field = `1/2 ε_0 (cB_0)^2 = 1/2 ε_0c^2B_0^2`
= `1/2 ε_0* 1/(mu_0ε_0) (B_0)^2` ......`[because c^2 = 1/(mu_0ε_0)]`
(Uav) electric field = `1/(2mu_0) B_0^2 (U_(av))_("magnetic field")`
Ratio = `((U_(av))_("electric field"))/((U_(av))_("magnetic field")) = 1/1`, i.e., 1:1
Hence the energy in electromagnetic wave is divided equally between electric field vector and magnetic field vector.
It means the ratio of contributions by the electric field and magnetic field components to the intensity of an electromagnetic wave is 1:1.
- When the incident EM wave is completely absorbed by a surface, it delivers energy u and momentum u/c to the surface.
- When a wave of energy u is totally reflected from the surface, the momentum delivered to surface is 2u/c.
APPEARS IN
RELATED QUESTIONS
To which part of the electromagnetic spectrum does a wave of frequency 5 × 1019 Hz belong?
What is the range of the wavelength of the following electromagnetic waves?
(a)X-rays,
Give one use of ultraviolet radiation.
Name the rays or waves of highest frequency .
Name three properties of ultraviolet radiations which are similar to visible light.
Characteristic X-rays may be used to identify the element from which they are being emitted. Can continuous X-rays be used for this purpose?
Why is exposure to X-rays injurious to health but not exposure to visible light, when both are electromagnetic waves?
The energy of a photon of a characteristic X-ray from a Coolidge tube comes from
The X-ray coming from a Coolidge tube has a cutoff wavelength of 80 pm. Find the kinetic energy of the electrons hitting the target.
(Use Planck constant h = 6.63 × 10-34 Js= 4.14 × 10-15 eVs, speed of light c = 3 × 108 m/s.)
Heat at the rate of 200 W is produced in an X-ray tube operating at 20 kV. Find the current in the circuit. Assume that only a small fraction of the kinetic energy of electrons is converted into X-rays.
Name the radiation which can be detected by thermopile.
Gamma rays and radio waves travel with the same velocity in free space. Distinguish between them in terms of their origin and the main application.
Name two sources of infrared radiation.
What are the ultraviolet rays?
Solve the numerical problem.
The speed of light is 3 × 108 m/s. Calculate the frequency of red light of a wavelength of 6.5 × 10−7 m.
The ozone layer absorbs
Identify the electromagnetic wave whose wavelength range is from about 10-12 m to about 10-8 m. Write one use of this.
Identify the electromagnetic wave whose wavelength range is from about 10-3 m to about 10-1 m. Write one use of this.
