24b3ikates please help me You and your friend Bruce are experimenting with a red

Question

24b3ikates

please help me

You and your friend Bruce are experimenting with a red lamp shade and blue lamp shade. You place lamp shades individually over a 120-W light bulb. Assume that the light radiates from the lamps uniformly and 7.1% of their power is converted to light.

(a) What is the average intensity of the light at 1.3 m from the red

(? = 710 nm)

lamp shade?
W/m2

(b) Is the average intensity of the blue

(? = 480 nm)

lamp shade at 1.0 m greater than, less than, or equal to the intensity calculated in part (a)?

greater thanless than    equal t

Explanation / Answer

a)

Inetnsity of the bulb is

I = P / A

= P / 4 pi r ^2

= 120 W / 4 pi ( 1.3 m )^2

= 5.65 W

b)

Intensity is independent on the wavelength of the bulb. it is directly proportional to the power of the bulb and inversely proportional to the square of the distance from the bulb to the point.

I = 120 W / 4pi ( 1 m ) ^2 = 9.54 W/m^2

Thus intensity of bulb at 1 m is greater than the intensity of bulb at 5m.

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