During a museum renovation, a conservator examines a faded painting under an angled glass cover. Fig. 1 shows a lamp, the glass, and the conservator's eye. ...
Question 1 Report
During a museum renovation, a conservator examines a faded painting under an angled glass cover. Fig. 1 shows a lamp, the glass, and the conservator's eye. The lamp produces a bright reflected patch that hides some detail in the picture. The glass surface is smooth, and the incident ray and normal are shown. The conservator wants to move the lamp, not the painting, so that reflected light misses the eye and the colours can be inspected.
(a) Calculate the angle of reflection if the angle of incidence is 28 degrees. [1]
(b) Draw the reflected ray that causes the bright patch. [2]
(c) Which direction should the lamp be moved to reduce the reflection into the eye: towards the normal or away from the normal? [1]
(d) Describe why the glare is produced by the glass. [2]
Answer Details
(a) By the law of reflection, the angle of reflection equals the angle of incidence. The angle of reflection is 28°. [1]
(b) The reflected ray is drawn on the opposite side of the normal, at 28° to the normal, and directed towards the eye. [2]
(c) The lamp should be moved away from the normal to change the reflected ray so that it misses the eye. [1]
(d) Smooth glass produces regular reflection. [1] The reflected rays can enter the eye and make a bright image of the lamp, causing glare. [1]
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