Question

The radius of curvature of a spherical mirror is 20 cm. Find its focal length.​

Answer 1

★ Question :-

∓ If the radius of curvature of a spherical mirror is 20 cm. Find its focal length .

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★ Answer :-

• Focal length of Mirror = 10 cm .

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★ Explanation :-

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✠ Given :-

• Radius of Curvature = 20 cm .

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✠ To Find :-

• Focal Length of the Mirror = ?

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✠ Solution :-

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∓ As we know ,

✪ Radius of Curvature = 2 × Focal Lenght

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∓ Then,

✪ Focal Length = $\large\sf{\frac{1}{2}}$× Radius of Curvature

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• Now, let's substitute -----

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➠ Focal Length = $\large\sf{\frac{1}{2}}$ × 20

➠ Focal Length = 1 × 10

➠ Focal Lenght = 10 cm .

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★ Hence :-

• Focal Length of Mirror = 10 cm .

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Answer 2

$\red \maltese \sf \: Given :-$

• Radius of curvature (R) = 20 cm

$\sf \red \maltese \: To \: Find : -$

• Focal length of the spherical mirror

$\sf \red \maltese \: Formula \: used :-$

$\bigstar \: \boxed{ \sf \: Radius \: of \: curvature = 2 \times focal \: length }$

$\sf \red \maltese \: Solution :-$

$\sf \dashrightarrow \: 20 \: cm \: = 2 \times f \\ \sf \dashrightarrow \: f = \frac{20 \: cm}{2} \: \: \: \: \: \: \: \: \\ \sf \dashrightarrow \: f = \frac{ \green{ \cancel{20}} \: ^{10} } {\green{ \cancel{ 2 }}\: \: ^{1} } \: \: \: \: \: \: \: \: \: \: \\ \sf \dashrightarrow \: f = 10 \: cm \: \: \: \: \: \: \: \: \:$

$\boxed {\sf \orange{ \therefore \: Focal \: length \: of \: the \: spherical \: mirror \: is \: 10 \: cm. }}$

$\red{ \rule{200pt}{}}$