Question

A perfectly reflecting body (sphere in shape) is placed on a path of parallel light beam of intensity I shown in figure. One end of a spring is attached to centre of sphere and the other end to a rigid wall as shown in figure. Sphere is in equilibrium. Spring constant of spring is K. Then compression in spring is –

(Radius of sphere is R)

(Neglect any thermal effect and friction is absent)

• A. $\frac{2I}{KC}\pi R^{2}$
• B. $\frac{I}{KC}\pi R^{2}$
• C. $\frac{I\pi R^{2}}{C}$
• D. None of these

Answer 1

Answer: (B)

$\frac{I}{KC}\pi R^{2}$

Answer 2

Kx₀ = $\frac{I}{C}(\pi R^{2})$, x₀ = $\frac{I}{KC}$ (pR²)