(a) If P bulb is the radiated power, and r is the radius of the circle, which expression gives the intensity, , within the illuminated region? Pbulb 4tr² Pbulb Tr² Pbulb 2πr (b) Which expression should you use to calculate the total incoming (received) power, Pin, over a square of side length, s, that is completely illuminated by the beam as shown in the above figure? stel Omile Ο Απί 70 X You shine the 13.5-cm radius circular beam of a 70-W flashlight on a square sticky-note with side length 8.1-cm that is tacked to a nearby wall as shown in the figure above. (c) What is the total (average) power received across the circular beam. W
(a) If P bulb is the radiated power, and r is the radius of the circle, which expression gives the intensity, , within the illuminated region? Pbulb 4tr² Pbulb Tr² Pbulb 2πr (b) Which expression should you use to calculate the total incoming (received) power, Pin, over a square of side length, s, that is completely illuminated by the beam as shown in the above figure? stel Omile Ο Απί 70 X You shine the 13.5-cm radius circular beam of a 70-W flashlight on a square sticky-note with side length 8.1-cm that is tacked to a nearby wall as shown in the figure above. (c) What is the total (average) power received across the circular beam. W
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Transcribed Image Text:Suppose that a flashlight beam spreads uniformly over a circular region as shown in the figure above.
(a) If P bulb is the radiated power, and r is the radius of the circle,
which expression gives the intensity, , within the illuminated region?
P bulb
4tr²
(b) Which expression should you use to calculate the total incoming (received) power, Pin, over a
square of side length, s, that is completely illuminated by the beam as shown in the above figure?
OP bulb
πtr²
Os²l πr² 04πr²✔
70
You shine the 13.5-cm radius circular beam of a 70-W flashlight on a square sticky-note
with side length 8.1-cm that is tacked to a nearby wall as shown in the figure above.
P bulb
2πr
(c) What is the total (average) power received across the circular beam.
2.01
W
(d) What is the total (average) power received across a sticky note?
x W
305.68
(d) What is the intensity of the incident light on the sticky note?
x W/m²
Transcribed Image Text:Intensity is a measure of incoming power per unit area.
If I is the intensity of the incoming energy within an
illuminated region of area, A, then the total received power is
given by:
P = JA
where I depends on the power of the radiating source, how it
spreads and how far away it is from the illuminated region.
Area, A
0
Intensity. I
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