Test: Characteristics of EM Waves - NEET MCQ

μ₀ is called the permeability of free space and similarly, ε₀ is called the permittivity of free space.

All regions have the same speed.
The speed of a wave is not dependent upon its frequency and wavelength but rather upon the properties of the medium through which it travels.
 

A gamma ray or gamma radiation is a penetrating electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves and so imparts the highest photon energy

Maxwell predicted that an accelerated charge produces a sinusoidal time varying magnetic field, which in turn produces a sinusoidal time varying electric field. These two fields are mutually perpendicular to each other and sources of each other. They (fields) form an electromagnetic wave i.e. the wave that is propagated by simultaneous periodic variations of electric field and magnetic field intensity.

In electromagnetic waves the ratio of amplitudes of electric field and magnetic field is equal to the velocity of the electromagnetic waves in free space.

(E₀ / B₀) = c

Electromagnetic waves are used in various applications such as:

• Detecting invisible writing (UV light)
• Keeping plants warm in greenhouses (infrared radiation)
• Enhancing vision in warfare (thermal imaging)

However, global warming is primarily caused by greenhouse gases trapping heat. This process involves electromagnetic waves indirectly through the greenhouse effect. Therefore, while electromagnetic waves contribute to the mechanisms of global warming, they are not directly used in the phenomenon itself.

Thus, option B is correct as it represents an effect rather than a direct application.

Red light has the lowest energy and is least scattered and has thus least frequency, thus we get that it has the largest wavelength. Similarly violet has maximum frequency.

V(velocity/speed)= ω/wave number (K)
V= 12×10¹⁵/4×10⁷
V=3×10⁸ m/s

The correct sequence of the radiation source in increasing order of the wavelength is Radioactive source (∼10⁻¹² m)→ X-ray tube (∼10⁻¹⁰ m)→ Sodium lamp (∼10⁻⁹ m)→ Magnetron value (∼10⁻³ m).,

The direction of propagation of electromagnetic wave is perpendicular to both electric field E and magnetic field B, i.e., in the direction of E×B by right thumb rule. The diagram given below

So, electromagnetic wave is along the z-direction which is give the cross product of E and B direction is
perpendicular to E and B from i.e., (E×B) in z− direction.