Question

If a 120-W lightbulb emits 3.5 % of the input energy as visible light (average wavelength 550 nm) uniformly in all directions.

How many photons per second of visible light will strike the pupil (4.0 mm diameter) of the eye of an observer 1.6 m away? Express your answer using two significant figures. ΔN1Δt Δ N 1 Δ t = photons/s SubmitPrevious AnswersRequest Answer Incorrect; Try Again; 5 attempts remaining Part B How many photons per second of visible light will strike the pupil (4.0 mm diameter) of the eye of an observer 1.3 km away? Express your answer using two significant figures. ΔN2Δt Δ N 2 Δ t = nothing photons/s SubmitRequest Answer

Answer #1

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If a 120-W lightbulb emits 2.5 % of the input energy as visible
light (average wavelength 550 nm) uniformly in all directions.
Part A. How many photons per second of visible light will strike
the pupil (4.0 mm diameter) of the eye of an observer 1.9 m away?
Answer in photons/s
Part B. How many photons per second of visible light will strike
the pupil (4.0 mm diameter) of the eye of an observer 1.5 km away?
Answer in photons/s

How many photons per second of visible light will strike the
pupil (4.0 mm diameter) of the eye of an observer 1.6 m away?
Express your answer using two significant figures. ΔN1Δt Δ N 1 Δ t
= photons/s SubmitPrevious AnswersRequest Answer Incorrect; Try
Again; 5 attempts remaining Part B How many photons per second of
visible light will strike the pupil (4.0 mm diameter) of the eye of
an observer 1.3 km away? Express your answer using two significant...

A 100-W incandescent lightbulb radiates visible light at a rate
of about 10.0 W; the rest of the EM radiation is mostly infrared.
Assume that the lightbulb radiates uniformly in all directions.
Under ideal conditions, the eye can see the lightbulb if at least
20.0 visible photons per second enter a dark-adapted eye with a
pupil diameter of 7 mm. Estimate how far from the source the
lightbulb can be seen under these rather extreme conditions. Assume
an average wavelength...

Assuming that 10.0% of a 100 W light bulb's energy output is in
the visible range (typical for incandescent bulbs) with an average
wavelength of 580 nm, and that the photons spread out uniformly and
are not absorbed by the atmosphere, how far away (in km) would you
be if 580 photons per second enter the 3.00 mm diameter pupil of
your eye? (This number easily stimulates the retina.)

Assuming that 10.0% of a 100 W light bulb's energy output is in
the visible range (typical for incandescent bulbs) with an average
wavelength of 580 nm, and that the photons spread out uniformly and
are not absorbed by the atmosphere, how far away (in km) would you
be if 414 photons per second enter the 3.30 mm diameter pupil of
your eye? (This number easily stimulates the retina.)

Assuming that 10.0% of a 100 W light bulb's energy output is in
the visible range (typical for incandescent bulbs) with an average
wavelength of 580 nm, and that the photons spread out uniformly and
are not absorbed by the atmosphere, how far away (in km) would you
be if 596 photons per second enter the 3.20 mm diameter pupil of
your eye? (This number easily stimulates the retina.)

The threshold of dark-adapted (scotopic) vision is 3.3 ?
10?11 W/m2 at a central wavelength of 500 nm.
If light with this intensity and wavelength enters the eye when the
pupil is open to its maximum diameter of 8.3 mm, how many photons
per second enter the eye?
photons/s

A small helium-neon laser emits red visible light with a power
of 5.90 mW in a beam that has a diameter of 2.60 mm .
A)What is the amplitude of the electric field of the light?
Express your answer with the appropriate units.
B)What is the amplitude of the magnetic field of the light?
C)
What is the average energy density associated with the electric
field?
Express your answer with the appropriate units.

We can reasonably model a 40 W incandescent lightbulb as a
sphere 5.0 cm in diameter. Typically, only about 5.0 % of the
energy goes to visible light; the rest goes largely to nonvisible
infrared radiation.
What is the visible light intensity (in W/m2) at the surface of
the bulb? Express your answer in watts per meter squared.
What is the amplitude of the electric field at this surface, for
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A green leaf has a surface area of 2.05 cm2.
If solar radiation is 1170 W/m2 , how many photons strike the
leaf every second? Assume three significant figures and an average
wavelength of 504 nm for solar radiation.
Express your answer using three significant figures.
N =
photons per second

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