Physics, asked by MssShreya, 1 year ago

A beam of light converges to a point P. Now a lens is placed on the path of the convergent beam 12 cm
from P. At what point does the beam converge if the lens is

(a) a convex lens of focal length 20 cm, (b) a concave lens of focal length 16 cm​

Answers

Answered by Anonymous
13

\huge\underline\purple{\sf Solution:}

a) A convex lens of focal Lenght 20cm :-

\large\underline\pink{\sf Given:- }

Distance of object from lens (u) = 12 cm

Focal Lenght of convex lens (f) = 20 cm

\large\underline\pink{\sf To\:Find:- }

Point at which beam converges (v) = ?

━━━━━━━━━━━━━━━━━━━━━━━━━

According to lens formula :-

\large{♡}\large{\boxed{\sf {\frac{1}{f}}={\frac{1}{v}}-{\frac{1}{u}}}}

\large{\sf {\frac{1}{v}}={\frac{1}{u}}+{\frac{1}{f}}}

\large\implies{\sf {\frac{1}{12}}+{\frac{1}{20}}}

\large\implies{\sf {\frac{60}{8}}}

\large\implies{\sf 7.5cm }

\huge\red{♡}\large\red{\boxed{\sf v=7.5cm }}

i.e. , the image is formed on the right of the lens and is real .

b) A concave lens of focal length 16 cm :-

\large\underline\pink{\sf Given:- }

Distance of object from lens (u) = 12 cm

focal length of concave lens (f) = 16 cm

\large\underline\pink{\sf To\:Find:- }

Point at which beam converges (v) = ?

━━━━━━━━━━━━━━━━━━━━━━━━━

According to Lens Formula :-

\large{♡}\large{\boxed{\sf {\frac{1}{f}}={\frac{1}{v}}-{\frac{1}{u}}}}

\large{\sf {\frac{1}{v}}={\frac{1}{f}}+{\frac{1}{u}}}

\large\implies{\sf {\frac{1}{-16}}+{\frac{1}{12}}}

\large\implies{\sf +48cm }

\huge\red{♡}\large\red{\boxed{\sf v=+48cm}}

i.e., The image is formed at 48 cm to the right of the lens where the beam would converge and is real

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Answered by Anonymous
9

❤Bonjour❤

Refer to the attachment!!

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