Question

an object 4cm in size is placed at 26 cm in front of a conacave mirror of focal length 15cm at what distance from the mirror would a screen be placed in order to obatain in sharp image? find the nature and the size of the image ​

Answer 1

Given

• Object Size = 4 cm
• Object Distance = -26 cm
• Mirror used = Concave
• Focal length = -15 cm

To Find

• Nature and size of the image

Solution

● Mirror Formula :- 1/v + 1/u = 1/f

● Magnification :- Hᵢ/Hₒ = -v/u

✭ Image Distance :

→ 1/v + 1/u = 1/f

→ 1/v + 1/-26 = 1/-15

→ 1/v - 1/26 = -1/15

→ 1/v = 1/26 - 1/15

→ 1/v = 15/390 - 26/390

→ 1/v = (15-26)/390

→ 1/v = 11/390

→ v = 390/11

→ v = 35.45 cm

✭ Size of the Image :

→ Hᵢ/Hₒ = -v/u

→ Hᵢ/4 = -(-35.45)/-25

→ Hᵢ = 35.45/25 × 4

→ Hᵢ = 5.672 cm

∴ The image is real, inverted placed at 35.45 cm and magnified