(4%) Problem 8: Electric room heaters use a concave mirror to reflect infrared (
ID: 1878403 • Letter: #
Question
(4%) Problem 8: Electric room heaters use a concave mirror to reflect infrared (IR) radiation from hot coils. Note that IR follows the same law of reflection as visible light. Find the magnification of the heater element, given that the mirror has a radius of curvature of 51 cm and produces an image of the coils 2.9 m away from the mirror Grade Summary Deductions Potential 0% 100% sin cotan) asin) Submissions tanO t ( acosO 78 9 Attempts remaining: S (10% per attempt) detailed view atan) acotan)sinh(0 cosh0nh cotanh0 Degrees O Radians 0 END CLEAR SubmitHnt I give u Hints: 4% deduction per hint. Hints remaining: 2 Feedback: 5% deduction per feedbackExplanation / Answer
R = radius of curvature of concave mirror = 51 cm
f = focal length of concave mirror = R/2 = 51/2 = 25.5 cm
di = image distance = 2.9 m = 290 cm
do = object distance = ?
Using the mirror equation
1/f = 1/di + 1/do
1/25.5 = 1/290 + 1/do
do = 28 cm
magnification is given as
m = - di/do
inserting the values
m = - (290/28)
m = - 10.4
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