Question

if the focal length of a concave mirror is 15 CM if an object is placed at a distance of 30 cm from the pole then its image will be formed at which​

Answer 1

$\huge{\red{\underline{\underline{\rm{Correct\;Question:}}}}}$

If the focal length of a concave mirror is 15 cm. If an object is placed at a distance of 30 cm from the pole. Calculate the position of image.

$\huge{\red{\underline{\underline{\rm{Solution:}}}}}$

$\large{\underline{\sf{Given:}}}$

$\sf{\implies Focal\;length\;(f)=-15\;cm}$

$\sf{\implies object\;distance\;(u)=-30\;cm}$

$\large{\underline{\sf{To\;Find:}}}$

$\sf{\implies\;Image\;distance\;of\;the\;mirror.}$

$\large{\underline{\sf{Formula\;used:}}}$

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

$\textsf{Now, put the values in the formula,}$

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

$\sf{\implies \dfrac{1}{-15}=\dfrac{1}{v}-\dfrac{1}{30}}$

$\sf{\implies -\dfrac{1}{15}+\dfrac{1}{30}=\dfrac{1}{v}}$

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

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

${\boxed{\boxed{\red{\sf{\implies v=-30\;cm}}}}}$

Hence, the image is places -30 cm from the mirror.

Answer 2

Solution:

Given:

➜ If the focal length of a concave mirror is 15 CM if an object is placed at a distance of 30 cm.

Find:

➜ From the pole then its image will be formed at which.

Find:

➜ Find the image distance of the mirror.

According to the given question:

➜ -15 cm = focal length.

➜ -30 = object distance.

Formula used:

➜ 1/f = 1/v + 1/u

Know terms:

➜ initial velocity (u)

➜ final velocity (v)

➜ focal length (f)

Adding values in the formula:

➜ 1/f = 1/v + 1/u

➜ 1/-15 = 1/v - 1/30

➜ -1/15 + 1/30 = 1/v

➜ -2 + 1/30 = 1/v

➜ -1/30 = 1/v

➜ v = -30 cm

Therefore, -30 cm is the image distance of the mirror.

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