List of top Physics Questions on Electromagnetic waves asked in CBSE CLASS XII

The magnetic field in a plane electromagnetic wave travelling in glass (\( n = 1.5 \)) is given by \[ B_y = (2 \times 10^{-7} \text{ T}) \sin(\alpha x + 1.5 \times 10^{11} t) \] where \( x \) is in metres and \( t \) is in seconds. The value of \( \alpha \) is:
Differentiate between conduction current and displacement current. A capacitor is connected across a source providing time-dependent current. Explain how the total current at an instant is the sum of conduction current and displacement current in the circuit at that instant.
Briefly explain how and where the displacement current exists during the charging of a capacitor.
Name the electromagnetic radiations and write their frequency range:
(a) Used to take the photograph of the bones
(b) Produced by hot bodies
(c) Used in television communication systems
Which of the following electromagnetic waves has photons of largest momentum?
The amplitude of electric field in an electromagnetic wave in free space is \( 1000 \, \text{Vm}^{-1} \). The amplitude of the magnetic field in this electromagnetic wave is:
State any three characteristics of electromagnetic waves.
In an electromagnetic wave travelling in free space, the amplitude of magnetic field is \( 6.0 \times 10^{-4} \ \text{T} \). The amplitude of its electric field is:
Name the electromagnetic wave used (i) in radar, (ii) in eye surgery, and (iii) as a diagnostic tool in medicine. Write their wavelength range also.
(a) How are electromagnetic waves produced?
(b) Write the wavelength range and one use of:
(i) Microwaves, and
(ii) Ultraviolet waves.
Which one of the following correctly represents the change in wave characteristics (all in vacuum) from microwaves to X-rays in electromagnetic spectrum?
In (A parallel plate capacitor is charged by an ac source. Show that the sum of conduction current Ic and the displacement current Id has the same value at all points of the circuit.), is Kirchhoff's first rule (junction rule) valid at each plate of the capacitor? Explain.
A parallel plate capacitor is charged by an ac source. Show that the sum of conduction current \( I_c \) and the displacement current \( I_d \) has the same value at all points of the circuit.