## Question

Two stars *P* and *Q* have slightly different surface temperatures *T _{P}* and

*T*respectively, with T

_{Q}_{P}> T

_{Q}. Both stars are receding from the earth with speeds

*v*and

_{P}*v*relative to the earth. The wavelength of light at which they radiate the maximum energy is found to be same for both:

_{Q}### Solution

Let and be the actual wavelength at which *P* and *Q* radiate maximum energy. By Wien’s law,

As these wavelengths appear equal on reaching the earth, has increased more than Hence

#### SIMILAR QUESTIONS

A bob of mass *m* is oscillating as a simple pendulum with maximum amplitude θ_{m}. What is the maximum tension in the string?

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In a resonance column experiment, a long tube, open at the top, is calmed vertically. By a separate device, water level inside the tube can be moved up or down. The section of the tube from the open end to the water level acts as a closed organ pipe. A vibrating tuning fork is held above the open end, and the water level is gradually pushed down. The first and the second resonances occur when the water level is 24.1 cm and 74.1 cm respectively below the open end. The diameter of the tube is: