You have a small frosted light bulb. There isanonreflecting surface behindthebulb.

a) The bulb is turnedon.Describe how the light intensity varies as you movefurther andfurther away from the light bulb.

b) Now the bulb isturnedoff, but light from a lamp is shined onto it.Describesimilarities and differences from (a) in the way thelightintensity varies as you move further and further away fromthebulb. Explain your answer.

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I already have part a and b, i just need help with c throughd

A regular light bulb emits electromagnetic waves of variouswavelengths (which makes the âwhiteâ light); in fact thedistribution of intensities is a continuous function of thewavelength (as in discussion of black body radiation). Thisdistribution, however, peaks at some characteristic wavelength. Inthe following assume that the entire power of the light bulb comesfrom emitting in this single characteristic wavelength. A lightbulb has power P=100W.

a) What is the intensity of the emitted light at a distance r=10mfrom the light bulb?
b) What is the amplitude of the electromagnetic field at thatdistance?
c) What is the average energy density of e.m. radiation at thedistance r=10m from
the light bulb.
d) What is the momentum transferred by this light to a small flatmirror with surface
area S=0.5m2 placed in front of the light bulb at the distancer=10m during the
time t=1s.
e) What it the pressure excreted by the light on the surface inpart d)

I already have part a and b, i just need help with c through d

The figure shows the interior of a three-way incandescent lightbulb, which provides three levels of light intensity. The socket of the lamp is equipped with a four-position switch for selecting different light intensities, with the positions described as follows: (1) off (switches S₁ and S₂ both open), (2) switch S₁ closed, (3) switch S₂ closed, and (4) switches S₁ and S₂ both closed. The lightbulb contains two filaments. When the lamp is connected to a 120-V source, one filament receives 100 W of power and the other receives 75 W. What is the total power input to the light bulb when (a) only switch S₁ is closed, (b) only switch S₂ is closed, and (c) both switches are closed? (d) What If? Suppose the 75-W filament breaks and no longer is able to carry a current. How many switch positions will result in the light leaving the bulb and what will be the power input to the bulb in those positions?

Figure

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Figure P27.3 shows the interior of a three-way incandescent lightbulb, which provides three levels of light intensity. The socket of the lamp is equipped with a four-position switch for selecting different light intensities, with the positions described as follows: (1) off (switches S₁ and S₂ both open), (2) switch S₁ closed, (3) switch S₂ closed, and (4) switches S₁ and S₂ both closed. The lightbulb contains two filaments. When the lamp is connected to a 120-V source, one filament receives 100 W of power and the other receives 75 W. What is the total power input to the light bulb when (a) only switch S₁ is closed, (b) only switch S₂ is closed, and (c) both switches are closed? (d) What If? Suppose the 75-W filament breaks and no longer is able to carry a current. How many switch positions will result in the light leaving the bulb and what will be the power input to the bulb in those positions?

Figure P27.3

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