JEE Mains Model Paper 12

P be the pole of concave mirror. C its centre of curvature and A be the point of incidence.
It is clear from the figure that ΔACF is an isosceles.
Hence CF = AF = CBsecθ =

1

2

CAsecθ =

R

2

secθ
∴ PF = CP - CF = R -

R

2

secθ = R (1−

secθ

2

)