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The angle between the reflected ray and the line perpendicular to the reflecting surface at the point of incidence is known as the angle of reflection.

The angle which incident ray makes with the perpendicular to the surface at the point of incidence.

A ray of light that strikes a surface or falls on a surface before being reflected, transmitted or absorbed is known as incident ray.

Normal is an imaginary line perpendicular to the surface, in the reflection of light from a plane mirror.

The point of incidence is the point where the incident ray strikes the mirror.

The light ray reflected by a surface, when an incident ray strikes the same surface is the reflected ray. The reflected ray corresponds to the incident ray always.

For a single incident ray falling on a plane mirror, there is always a single reflected ray. The angle of incidence is always equal to the angle of reflection, this is by the law of reflection.

Formula : 

Number of images N = \(\frac{360°}{30°} - 1\)

Gvien :

θ = 30°

 N = \(\frac{360°}{30°} - 1\)

= 12 - 1 = 11 images.

Light is splitted into its constituent colours, when it gets dispersed.

Example:

Rainbow formation is due to the dispersion of white light after passing through water droplets.

Light is split into its constituent colours. Rainbow is an example.

Image is small in and closure.

c) 30 degree

The correct answer is No .

(a) A person 1 m in front of a plane mirror seems to be 2 m away from his image. 

(b) If you touch your left ear with your right hand in front of a plane mirror, it will be seen in the mirror that your right ear is touched with your left hand. 

(c) The size of the pupil becomes large when you see in dim light. 

(d) Night birds have less cones than rods in their eyes.

This is called  Lateral inversion.

When you are eating food with right hand it appears to be eating with left hand in a mirror. Such a shift of lateral side of images in opposite direction is called lateral inversion. Images formed by plane mirrors undergo lateral inversion.

CD reflects rainbow colours, and interesting : patterns.

Left hand of the mirror image is raised.

The height remains the same.

Incident ray – Light which falls on the mirror/ polished surface is called incident ray.

Following are the Cartesian sign conventions for spherical mirror:

• All distances are measured from the pole of the mirror.
• Incident light is shown coming from LHS of mirror.
• Distances towards LHS of mirror are taken as negative and those on RHS are taken as positive.
• The height is measured perpendicular to the principal axis.
• Distance above principal axis is taken as positive.
• Distance below principal axis is taken as negative.

Types of convex lens: Biconvex lens, piano-convex lens, concavo-convex lens 

Types of concave lens: Biconcave lens, plano-concave lens, convexo-concave lens

When a ray of light travels from one medium to another medium there is a deviation in its path. This phenomenon is called refraction of light. 

Following are the laws of refraction:

• When a ray of light travels from a rarer medium to a denser medium, it bends towards the normal.
• When a ray of light travels from a denser medium to a rarer medium, it bends away from the normal.
• Ratio of sine of angle of incident to sine of angle refraction is constant for a given pair of media. This is called Snell’s law.

Following are the laws of refraction through spherical lens:

• A ray parallel to the principal axis passes through main focus after refraction through lens.
• A ray passing through focus of the lens becomes parallel to principal axis after refraction.
• A ray passing through optical centre emerges without deviation.

The change in direction of light, when it travels from one medium to another medium is called refraction of light.

(d) Dispersion of light

Correct answer is (d) Iris

An object absorbs all the colours of light falling on it. This object would appear of Black colour.

(d) All of the above.

(b) refraction

c) Dispersion

Correct answer is (c) 25 cm

Rainbow is always formed in the direction opposite to sun. The position of red colour in the rainbow is at the top.

Sun appears red during sunset or sunrise because at this time the sun is far from the earth and the light that reaches the earth from the sun scatters the most and all other colours of light gets scattered. The least scattered light is red and it enters our eye.

When sun light splits due to water drops suspended in air, causing the band of seven colours is called rainbow. Water droplets acts as tiny prism in the sky. The sunlight when enters these tiny droplets undergo internal reflection and also refract these rays which are dispersed causing a band of seven colours called rainbow. Rainbow is always formed in the direction opposite to the sun.

Power of Accommodation: Human eye can see nearby objects as well as distant objects. Our eyes can quickly focus from a nearby object to a distant object. This is called power of accommodation. 

Field of Vision: The extent of observable world which can be seen by both eyes at a given moment is called field of vision. The field of vision with both eyes is slightly more than 180 degrees.

Danger signals are of red colour, as it scatters the least and can be seen from the maximum distance.

In Myopia type of eye defect far point of the eye gets reduced.

The amount of light entering the eye is controlled by the pupil and further the size of the pupil is controlled by iris.

Correct answer is (b) Pupil

D. iris 

The muscles of the iris dilate and constrict the pupil and thus increases and reduces the amount of light entering the eye.

(a) Iris controls the amount of light entering the eye by constricting and dilating the pupil in bright and dim light respectively. 

(b) Lens. The lens may diverge or converge the light rays to form an image. 

(c) Retina. An upside-down image is formed on the retina. 

(d) Optic nerve carries the image to brain in form of electric impulses. 

(e) Ciliary muscle changes the lens shape to focus objects lying at various distances.

(a) Cones are sensitive to bright light. Cone shaped cells present in the retina are sensitive to bright light. 

(b) Rods are sensitive to dim light. Rod shaped cells present in the retina are sensitive to dim light. They are most important for vision in dim light 

(c) Cones are the cells of retina that produce color sensation. These photo receptor cells are responsible for color vision.

In dim light the size of the pupil of our eye becomes larger or dilates to increase the amount of light going inside the eye. This dilation in size is facilitated by the muscles of iris.