Question #174

This week we consider a second question regarding the Crooke's radiometer. Please refer to the previous question for background information.

We have seen that even if only the black sides of the radiometer vanes are illuminated by the heat lamp the radiometer spins with very nearly the same angular speed as if both sides were illuminated.

This week the question involves the white side of the vane, which we will illuminate for this experiment, as seen in the photograph below, by sliding the white cardboard shield to the opposite side of the device.

If only the white side of the radiometer is illuminated, the radiometer will:

• (a) rotate about the same speed as when both sides are illuminated.
• (b) rotate significantly more slowly than when both sides of the vanes are illuminated.
• (c) remain motionless.
• (d) rotate in the opposite direction.

Click here for Answer #174 after February 9, 2004.

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