Question

student is conducting an experiment with concave mirror of focal length 10 cm. Find position of
e image when object is placed at 20 cm
15 cm
B) 20 cm
C) 25 cm
D) 5 cm​

Answer 1

Answer:

Concave mirror

u=-20

f=-10

1/f=1/v+1/u

1/-10=1/v+1/-20

1/v=1/20-1/10

1/v=1-2/20

1/v=-1/20

v=-20

image is formed 20cm from the pole in front of the lens

nature:

m=-v/u

=-(-20)/-20

=-1

so the image is real, inverted and same size image

Answer 2

$\large\bf\underline \blue {To \: \mathscr{f}ind:-}$

• we need to find position of image.

$\huge\bf\underline \red{ \mathcal{S}olution:-}$

$\bf\underline{\purple{Given:-}}$

• Focal length (f) = -10cm
• Object distance (u) = -20cm
• image distance (v) = ?

• By using mirror Formula :-

$\bf\star \green{ \huge\frac{1}{v} + \frac{1}{u} = \frac{1}{f} }$

↛ 1/v = 1/f - 1/u

↛ 1/v = 1/-10 - 1/-20

↛ 1/v = -1/10 + 1/20

↛ 1/v = (-2 + 1)/20

↛ 1/v = -1/20

↛ - v = 20

↛ v = -20cm

Hence,

• Image distance is -20cm

If image distance is negative then, The image formed is real in front of the mirror.

We can also find the Nature of image by magnification

• Magnification = -v/u

⪼ m = -(-20)/-20

⪼ m = 20/-20

≫ m = -1

So,

Magnification is negative when image is inverted .

━━━━━━━━━━━━━━━━━━━━━━━━━