Question

An inverted image is required of height 12 cm of an object kept at a distance of 20 cm from a concave mirror. The focal Length of the mirror is 15 cm. At what distance from the mirror should a screen be kept so as to get a clear image? What will be the size and nature of the image?

Answer 1

Explanation:

सॉलिड बॉडी ऑफ मास 200 ग्राम एंड वॉल्यूम 3 सीसी इन इनपुट इन वॉटर will it float or sink

Answer 2

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It is given that :-

• Height of object = 12cm
• Object distance = 20cm
• Focal length of mirror = 15cm
• Image distance = ?
• Height of image = ?

Now, we know according to mirror formula :-

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

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

After inputting the known values we get :-

$15 = \frac{ - 20v}{20 - v}$

$300 - 15v = - 20v$

$300 = - 20v + 15v$

$300 = 5v \\ \\ v = \frac{300}{5} \\ \\ v = 60cm$

Therefore at a distance of 60cm from mirror a screen should be kept to obtain a sharp image.

Now we know that :-

$\frac{h_i}{h_o} = \frac{ - v}{u}$

After inputting the values we get :-

$\frac{h_i }{12} = \frac{ - 60}{20}$

$\frac{h_i}{12} = - 3$

$h_i = - 3 \times 12 = - 36cm$

Therefore the size of image formed will be 36cm.

Now we can see that :- Size of image > Size of object.

Therefore the image is magnified and concave mirror always produces inverted and real image.

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BY SCIVIBHANSHU

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