Question

The radius of curvature of a concave mirror is 20cm. An object is placed at a distance of 15cm from a concave mirror. Finde the distance of image .​

Answer 1

Given Data:

R = 20cm, f = R/2 =10cm

P = ? (Distance of the object)

q =2p (from definition of magnification)

Formula for concave mirror is

1/f = 1/p + 1/q

1/f = 1/p + 1/2p

1/f = 3/2p

P = 3f/2 =(3×10cm)/2

P = 15cm

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your answer is 15 cm

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Answer 2

Given:

$\sf{Radius \:of \:Curvature=-20cm}$

$\sf{\therefore Focal \:length=-10cm}$

$\sf{Object \:Distance=-15cm}$

$\sf{Mirror=Concave \:mirror}$

To Find:

$\sf{Distance \:of \:image \:from \:mirror}$

Solution:

$\sf{{\dfrac{1}{f}}={\dfrac{1}{v}}+{\dfrac{1}{u}}}$

$\sf{-{\dfrac{1}{10}}={\dfrac{1}{v}}-{\dfrac{1}{15}}}$

$\sf{{\dfrac{1}{v}}=-{\dfrac{1}{10}}+{\dfrac{1}{15}}}$

$\sf{{\dfrac{1}{v}}={\dfrac{-3+2}{30}}}$

$\sf{{\dfrac{1}{v}}=-{\dfrac{1}{30}}}$

$\sf{{v=-30cm}$

Thus, the image will be formed at 30cm from the pole of concave mirror and will be at the same side where the object is kept.