Question

# $$(a)$$ Find the angle of incidence.$$(b)$$ Find the angle between the incident and reflected rays.Figure shows an incident ray $$AO$$ and the normal $$ON$$ on a plane mirror. The angle which the incident ray $$AO$$ makes with a mirror is $$30^{\circ}$$.

A
(a)60,(b)60
B
(a)120,(b)120
C
(a)60,(b)120
D
(a)120,(b)60

Solution

## The correct option is B $$(a) 60^{\circ}, (b) 120^{\circ}$$We know that angle of incidence and angle of reflection both are measured from normal which is perpendicular to the plane.Let,Angle of incidence $$=i$$Angle of reflection $$=r$$Normal ON is perpendicular to plane.So, angle of incidence, $$i=90^0 - 30^0= 60^0$$We know that angle of incidence$$=$$angle of reflectionSo, angle of incidence$$=$$angle of reflection $$=$$$${60}^{0}$$Hence, angle between incident ray(AO) and reflected ray(OB) is $$=i+r=60^0 + 60^0 = 120^0$$Physics

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