Question

A rod of length 5cm lies along the principal axis of the concave mirror of focal length 15cm in such a
way that the end of the closer to the pole is 30cm away from it. Then the length of the image —
(1) 2.75 cm (2) 3.75 cm
(3) 4.75 cm (4) None of the above​

Answer 1

Answer:

(2) 3.75 cm

Explanation:

Since we know,

u1 = -30 cm,

f = -15 cm

v1 = $\frac{u_{1} f}{u_{1} - f}$ = –30 cm

Also, since u2 = –35 cm from figure,

v2= $\frac{u_{2} f}{u_{2} - f}$ = –26.25 cm

|v1|–|v2| = 3.75 cm would be the length of the image