Science Olympiad Test: Light- 1 - Class 10 MCQ

A concave mirror has a reflective surface that is curved inward and away from the light source. Concave mirrors reflect light inward to one focal point. Unlike convex mirrors, the image formed by a concave mirror shows different image types depending on the distance between the object and the mirror.

 ∠AON = i = 30° = r = ∠ NOB
Ray AA´ deviates such that angle of

Deviation ∠ A´OB = 180° – 30° – 30° = 120°

m = -v/u. For a convex mirror, v is –ive, thus m becomes positive.

• Real Images are images which can be obtained on the screen. They are formed when light rays after getting reflected from a mirror actually meet at a point. 
• Virtual Images are images which can only be seen in a mirror but cannot be obtained on the screen. They are formed when light rays after getting reflected from a mirror appear to meet at a point. 

Given that u = - 20 cm and m = - 5

- 20 = - v/-5
v = - 4
Thus, the height of the object is 4 cm.

u = – 2 f    
= – 2 × 15
= – 30 cm

P = P₁ + P₂ = 4 D + (– 10 D) = – 6 D

u + v = 3 m (given)
As maximum distance between an object and image in case of a convex lens = 4 f
4 f = 3 m ⇒ f = 3/4 m = 0.75 m

In a convex lens, when object is in front of the lens at 2 F₁, an inverted image of size of object (h₂ = h₁) is formed at 2F₂. Therefore, m = – 1.

The refractive index of liquid must be greater than or equal to 1.5 in order to make the lens disappear.