Question

with the uses of mirrors formula find :u,when v=20 cm and f=5cm in concave mirror
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Answer 1

Answer:

u=20÷3

Explanation:

1÷5=1÷20+1÷u

1÷5-1÷20=1÷u

4÷20-1÷20=1÷u

3÷20=1÷u

u=20÷3

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Answer 2

Answer:

Explanation:

ANSWER:-

Given:-

• Image distance = 20 cm
• Focal Length = 5 cm
• And also, in case of concave mirror.

We know that:-

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

• We will take image negative as it is situated greater distance than focal length.
• The image formed is real and inverted so the fifth case.

$\dfrac{1}{5} = \dfrac{1}{-20}+\dfrac{1}{u}$

$\dfrac{1}{u} = \dfrac{1}{5}+\dfrac{1}{20}$

$\dfrac{1}{u} = \dfrac{1+4}{2}$

$\dfrac{1}{u} = \dfrac{5}{20}$

$\sf{Object \ Distance = 5 \ cm}$

Uses of Concave Mirror:-

• It is used in solar panels.
• It is used in solar cookers to trap heat.
• It is used as make up mirror and shaving mirrors.
• It is also used by dentists for closer view of teeth.
• The common application is for closer view of the object.
• The last case is used where the image is virtual.