Olympiad Test: Light - Free MCQ with solutions Class 8 Science

When light is incident on a rough surface, irregular reflection takes place, hence the image formed is not clear.

Glasses are coated with silver to be used as mirrors to increase their reflection property.

The phenomenon of light in which, light is reflected or bounced back into the same medium is called reflection.

The perpendicular drawn to the reflecting surface of a mirror at the point of incidence is called 'normal'. The point on the reflecting surface where the light ray is incident is called the point of incidence.

When two mirrors are kept parallel to each other, an infinite number of images can be seen.

The angle of incidence = the angle of reflection. So, the angle of reflection is 80^o.

A concave mirror is used by E.N.T. doctors to get a magnified image of internal organs like ear, nose and throat.

• To determine the number of images formed by two plane mirrors placed at an angle θ,

           we use the formula: n = (360/θ) - 1,

           where n is the number of images.

• For θ = 60°, the calculation is n = (360/60) - 1 = 6 - 1 = 5.
• Therefore, 5 images are formed.

In reflection of light, ∠i = 50^oand ∠i = ∠r = the angle between incident ray and reflected ray = 50° + 50° = 100°

We use plane mirrors to see ourselves, because the image formed by a plane mirror is virtual, erect and of the same size.

When a light ray is reflected from the reflecting surface, the incident ray, the reflected ray and the normal lie in the same plane. The angle of incidence = The angle of reflection.

The image formed by the plane mirror is laterally inverted i.e., the right side of the object appears on the left side of the image and left side of the object appears on the right side of the image.

Correct Answer :-B

Explanation:- A periscope is an optical instrument used to view object which is not in direct sight of human eye. It works by using the Laws of Reflection and are widely used in submarines to navigate under water. 

It works by using two mirrors placed at angle of 45 degree with each other. When light falls on one mirror, it bounces to the other mirror and then reaches the human eye.

A simple periscope only uses mirrors but complex periscope uses prisms instead of mirror. These periscopes are used in the field of medicine particularly in cystoscopy and endoscopy.

The human eye serves as a convex lens. It forms real, inverted and diminished image of an object.

Persistence of vision is a phenomenon where the brain continues to sense the image even after the object has been removed. This lasts for 1/16th of a second.

Cataract occurs in old age due to the given characteristics and can be cured by introducing a new artificial lens.

The nocturnal animals need more light to see at night. The large cornea and pupil allow more light to enter into their eyes. They also have retina with large number of rods.

∠i = 40^o(given) ∠i = ∠r = 40^o
The angle between the incident ray and the reflected ray =∠i +∠r = 40^o+40^o = 80^o

We know that for a reflected ray, the angle that the incident ray makes with the line perpendicular to the surface is equal to the angle made by the reflected ray with this perpendicular line. N is the correct reflected ray of X.