31 Year NEET Previous Questions: Electromagnetic Waves Free MCQ Practice

Rays  -    Wavelength
[Range in m]
X-rays    -  1 × 10^–11 to 3 × 10^–8
γ-rays     -  6 × 10^–14 to 1 × 10^–11
Microwaves    -  10^–3 to 0.3
Radiowaves    -  10 to 10⁴

Wavelength of red light is longest

X-rays are used for the investigation of
structure of solids

Sea waves travel in a straight line thus, they can only be used for in line communication. Whereas sky waves and ground waves are used for larger distances.

The direction of oscillations of E and B fields are perpendicular to each other as well as to the direction of propagation. So, electromagnetic waves are transverse in nature. The electric and magnetic fields oscillate in same phase.

Rays  -    Wavelength
[Range in m]
X-rays    -  1 × 10^–11 to 3 × 10^–8
γ-rays     -  6 × 10^–14 to 1 × 10^–11
Microwaves    -  10^–3 to 0.3
Radiowaves    -  10 to 10⁴

We know that velocity of  lectromagnetic
wave in vacuum 

velocity of electromagnetic wave in
medium is (v) =

Therefore refractive index of the medium

Initially there is no D.C. current in inductive circuit and maximum D.C. current is in capacitive current. Hence, the current is zero in A₂ and maximum in A₁.

A stationary charge produces electric field only; an uniformly moving charge produces localised electromagnetic field; an accelerated charge produces electromagnetic radiations.

Gamma rays have the lowest wavelength and therefore the highest frequency.

Ultraviolet rays have the highest wavelength and thus the lowest frequency.

Therefore, the order of frequency is: b > a > c.

α rays contain Helium nuclei which contains 2 unit of positive charge.

Direction of propagation of electro-magnetic waves is perpendicular to Electric field and Magnetic field. Hence, direction is given by

Gamma ray has highest frequency and lowest wavelength.

Infrared rays is the cause of Green house effect. The glass transmits visible light and short infrared rays which are absorbed by plants. Then it emits long infrared rays, which are reflected back by glass.

β ray is not electromagnetic ray

Depends on the magnitude of frequency

Option B is correct.

X-rays have wavelengths typically in the range 10^-11 m to 10^-8 m, much smaller than visible wavelengths.

Visible light wavelengths lie approximately in the range 4×10^-7 m to 7×10^-7 m.

Microwaves have wavelengths roughly in the range 10^-4 m to 10^-1 m, much larger than visible wavelengths.

Arranging these from largest to smallest gives λ_m > λ_v > λ_x, which corresponds to Option B.

Variation in magnetic field causes electric field and vice-versa.
In electromagnetic waves, .
Both  and    are in the same phase.
In electromagnetic waves
E = E0 sin(ωt - kx)
B = B0 sin(ωt - kx)
The electromagnetic waves travel in the
direction of 

The velocity of electromagnetic radiation
in a medium of permittivity  ∈₀ and
permeability μ₀ is equal to 

Comparing with the equation of wave

Electromagnetic waves are the combination of mutually perpendicular electric and magnetic fields. So, option (c) is false.

The electromagnetic wave is propagating along the +z axis.
Since the electric and magnetic fields are perpendicular to each other and also perpendicular to the direction of propagation of wave.
Also. gives the direction of wave propagation.

The decreasing order of the wavelengths is as given below :
microwave, infrared, ultraviolet, gamma
rays.

On comparing the given equation to

The average energy stored in the electric field 

The average energy stored in the magnetic field 

According to conservation of energy

Given: frequency f = 2MHz, relative
permittivity ∈_r= 4

From formula,

velocity 

[Since frequency remains unchanged]