Question

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Answer 1

Answer:

U=50cm F=20cm

Lens Formula

$\frac{1}{f} = \frac{1}{v} - \frac{1}{u}$

$\frac{1}{20} = \frac{1}{v} - ( - \frac{1}{50} )$

$\frac{1}{20} - \frac{1}{50} = \frac{1}{v}$

$\frac{3 - 2}{100} = \frac{1}{v}$

$v = \frac{100}{3}$

Object is Real and Inverted

Explanation:

Hope it will help you

Jai Hind

Answer 2

➠ Questíon :-

➝ An object is placed at a distance of 50cm from a concave lens of Focal length 20cm .find the nature and position of the image.

➠ Gíven :-

➝ Object distance, u = -50cm

➝ Focal length, f = -20cm

➠ To fínd :-

➝ the nature and position of the image

➠ Formula requíred :-

$\longrightarrow \boxed{\bf \frac{1}{f} = \frac{1}{v} - \frac{1}{u}}$

where,

⇢f = focal length

⇢v = Image distance

⇢u = object distance

➠ Solutíon :-

using lens formula,

$\longrightarrow \tt \: \: \frac{1}{v} - \frac{1}{u} = \frac{1}{f}$

$\longrightarrow \tt \frac{1}{v} - \frac{1}{ - 50} = \frac{1}{ - 20}$

$\longrightarrow \tt \frac{1}{v} + \frac{1}{50} = - \frac{1}{20}$

$\longrightarrow \tt \frac{1}{v} = - \frac{1}{20} - \frac{1}{50}$

$\longrightarrow \tt \frac{1}{v} = \frac{ - 5 - 2}{100}$

$\longrightarrow \tt \frac{1}{v} = \frac{ - 7}{100}$

$\longrightarrow \tt v = - \frac{100}{7}$

$\longrightarrow \boxed{ \tt v = - 14.3cm}$

Thus, the image is formed at the distance of 14.3cm from the concave lens.

→ Nature of the image is virtual and erect.

Note :-

◉ The minus sign of the image distance shows the image is formed on the left side of the concave lens

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➠ Additional information....

➤ What is focal length ?

• Focal Length and Angle of view. The focal length of the lens is the distance between the lens and the image sensor when the subject is in focus, usually stated in millimeters.

➤ What are the uses of concave lens ?

• Concave lenses are used in telescope and binoculars to magnify objects.
• As a convex lens creates blurs and distortion, telescope and binocular manufacturers install concave lenses before or in the eyepiece so that a person can focus more clearly.