Estimate the radiation pressure due to a bulb that emits 25 W of EM radiation at a distance of 7.5 cm from the center of the bulb. Assume that light is completely absorbed.

Given Information:

Wattage of bulb = W = 25 W

distance = d = 7.5 cm = 0.075 m

Required Information:

Radiation Pressure = ?

Radiation Pressure = 1.179x10⁻⁶ N/m²

Explanation:

The radiation pressure is given by

P = I/c

Where c = 299792458 m/s is the speed of light and I is the intensity of radiation and given by

I = W/4πd²

Where W is the wattage of bulb and d is the distance

I = 25/4π*0.075²

I = 353.67 w/m²

so the radiation pressure becomes

P = 353.67/299792458

P = 1.179x10⁻⁶ N/m²

Therefore, the radiation pressure due to a 25 W bulb at a distance of 7.5 cm is 1.179x10⁻⁶ N/m²

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

we don't care about the 150kg or the 2,500 meters. they don't make any difference.

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