In electromagnetic waves, the electric and magnetic fields are: MCQ with Answer and Explanation

In electromagnetic waves, the electric and magnetic fields are:
A. Perpendicular to each other and to direction of propagation
B. Parallel to each other and to direction of propagation
C. Parallel to each other but perpendicular to propagation
D. Randomly oriented
Answer: Option A
Solution (By JKSSB Mock Tests)
Electromagnetic waves are transverse: electric field (E) and magnetic field (B) are perpendicular to each other and both perpendicular to the direction of wave propagation. This is a fundamental property derived from Maxwell's equations. Memory tip: 'EM waves: E ⊥ B ⊥ propagation direction; right-hand rule for orientation'. This conceptual question tests electromagnetic wave fundamentals, crucial for modern physics in competitive exams. Always recall that EM waves require no medium and travel at speed of light in vacuum.

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Practice More Physics Questions

Question #1
If the random error in measurement of radius of a sphere is 2%, the error in volume is
A. 8%
B. 4%
C. 2%
D. 6%

Correct Answer: Option D


Explanation:
Volume V = (4/3)πr³. Fractional error ΔV/V = 3 Δr/r. Percentage error = 3 × 2% = 6%. Important for error analysis in competitive exams.

This question belongs to: Science Physics
Question #2
The buoyant force on an object immersed in a fluid depends on
A. Shape of the container
B. Density of the object
C. Depth of immersion
D. Density of the fluid and volume of displaced fluid

Correct Answer: Option D


Explanation:
Buoyant force = weight of displaced fluid = ρ_fluid × V_displaced × g. Independent of depth (if fluid incompressible) and object's density, though object density determines if it floats. Shape affects volume displaced when floating.

This question belongs to: Science Physics
Question #3
The gravitational force between two masses is F. If the distance between them is halved, the force becomes
A. 2F
B. F/2
C. F/4
D. 4F

Correct Answer: Option D


Explanation:
Newton's law of gravitation: F ∝ 1/r². If distance r becomes r/2, new force F' ∝ 1/(r/2)² = 4/r² = 4F. So force quadruples. This inverse square law is fundamental for gravitational, electric, magnetic forces.

This question belongs to: Science Physics