Question

A beam of light travelling along X-axis is described by the electric field Ey = 900sin ω(t - x/c). The ratio of electric force to magnetic force on a charge q moving along Y-axis with a speed of 3 × 107 ms-1 will be :
(Given speed of light = 3 × 108 ms-1)

• A. 1 : 1
• B. 1 : 10
• C. 10 : 1
• D. 1 : 2

Answer 1

Answer: (C)

10 : 1

Answer 2

Ratio $=\frac{|q\stackrel{→}{E}|}{|q\stackrel{→}{v}×\stackrel{→}{B}|}$

$=\frac{E}{v_B}=\frac{v_{wave}}{v}$

$⇒$Ratio $=\frac{3×10^8}{3×10^7}=\frac{10}1$

Therefore, The correct answer is (C) : $10:1$