Question

Estimate the radiation pressure due to a bulb that emits 25 W of EM radiation at a distance of 9.5 cm from the center of the bulb. Assume that light is completely absorbed. Express your answer to two significant figures and include the appropriate units.

Answer 1

Given Information:  

Power of bulb = w = 25 W atts

distance = d = 9.5 cm = 0.095 m

Required Information:  

Radiation Pressure = ?

Answer:

Radiation Pressure =7.34x10⁻⁷ N/m²

Explanation:

We know that radiation pressure is given by

P = I/c

Where I is the intensity of radiation and is given by

I = w/4πd²

Where w is the power of the bulb in watts and d is the distance from the center of the bulb.

So the radiation pressure becomes

P = w/c4πd²

Where c = 3x10⁸ m/s is the speed of light

P = 25/(3x10⁸*4*π*0.095²)

P = 7.34x10⁻⁷ N/m²

Therefore, the radiation pressure due to a 25 W bulb at a distance of 9.5 cm from the center of the bulb is 7.34x10⁻⁷ N/m²