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(a) Cone cell are sensitive to bright light.

(b) Rod cell are sensitive to dim light.

The inverted image is formed due to the eye lens which is convex in shape. Through which the incident light rays form the real and inverted image.

The image formed in a pinhole camera is  inverted .

Correct answer is (c) at C

(c) between P and F

(a) True

(b) False

(c) False

Concave mirror

B. virtual, behind the mirror and of the same size as the object. 

The images formed by a plane mirror are virtual, opposite in direction and are of the same size as the object.

(b) virtual, behind the mirror and of the same size as the object.

i. transparent

ii. opaque

iii. translucent

iv. opaque, through

v. long, short

We can take care of eyes by: 

→ Visit an eye specialist regularly. 

→ Avoid reading in dim light and very bright light. 

→ Avoid direct exposure of sunlight to the eye. 

→ Clean your eyes with cold water quickly if dust particles or small insects enter your eye. Do not rub your eyes. 

→ Maintain a distance of at least 25 cm between the book and your eyes while reading.

Laser light is harmful for the human eyes, because its intensity is very high. It can cause damage to the retina and lead to blindness. Hence, it is advisable not to look at a laser beam directly.

The Right option is : (a) A 

(a) True. Moon is a non-luminous object. It does not have light of its own, it reflects the light of sun and it is an illuminated object.

(b) False. Diffuse reflection does not mean the failure of laws of reflection of light. Diffused reflection is caused by the irregularity of a surface. 

(c) True. The pattern once seen through the eye hole can never be seen again in a kaleidoscope. The mirrors in the tube and the colored glass pieces continuously make different patterns.

1. False

2. False

3. False

4. True

5. False

All objects reflect light rays, but the best reflectors of light are mirrors, still water in a lake, new steel dish i.e. smooth shiny surfaces.

Optic nerve: Also called cranial nerve II (second cranial nerve). The optic nerve is present in the back of the eye. The function of the optic nerve is to transfer visual information from the retina to the vision centers of the brain. The information is carried in the form of electrical impulses.

Retina:

The retina is the membrane (tissue) that covers most of the inner surface of the eyeball. It contains hundreds of millions of light-sensitive cells, called cones and rods. Rod and cone cells are also called receptors (or photoreceptors). When a ray of light is falling on the retina, the cells present over the retina get activated and convert it into nervous signals (electrical impulse) which are transported to visual centers in the brain by the optic nerve.

Sources like sun, stars emit light on their own. 

Sources like bulb, torch light, candle do not emit light on their own.

Persistence of Vision- The property of this phenomenon is that the image formed on the retina of the eye persists for about 1/16th of a second, hence if 16 frames are shown on a screen in succession, they are viewed by the retina as an ongoing action.

The phenomenon that applies here is multiple reflection that provides the image of back of the head to be viewed. A person is made to stand in front of a mirror and another mirror is held at the back of the head. The reflection from the mirror at the back is visible in the mirror in front of the person and hence the hair at the back of the head is visible to the person in the front mirror.

1. A periscope is used to see over, through or around any object. 

2. It can be used to see over a wall, to see around a corner. 

3. Periscopes are also used in warfare to keep an eye on the enemy.

A mirror whose polished, reflecting surface is a part of a hollow sphere of glass or plastic is called a spherical mirror.

A periscope is a device that reflects the reflected ray again. It consists of a tube attached to a set of mirrors. 

There are 2 mirrors in a periscope.

The light from the object falls on one mirror that is placed at 45o to the object and the light gets reflected. This reflected light in turn falls on another mirror and is again reflected until it reaches the eyepiece.

Given the angle between the two plane mirror = 60°

Number of the image formed = \(\frac{360}{angle\,between\,the\,plane\,mirror}-1\)

So number of image will be = \(\frac{360}{60}-1\)

= 6 – 1

= 5

a) The 2 plane mirrors are parallel to one another. 

b) The plane mirrors make an angle of 45 degrees with respect to the sides of the tube.

Periscope is one such device which works on the reflection of reflected light.

The light from the object falls on one mirror that is placed at 450 to the object and the light gets reflected. This reflected light in turn falls on another mirror and is again reflected until it reaches the eyepiece.

The correct option is B) 5.

The correct option is D) 3.

C. periscope 

Periscopes are used to see objects that are not in direct line of sight.

The correct option is A) infinity.

The reflection at any plane surface is found to obey the laws of reflection. 

The laws of reflection are:

The incident ray, the reflected ray and the normal at the point of incidence all lie in the same plane.

The angle of incidence is equal to the angle of reflection.

The phenomenon by which a ray of light changes the direction of propagation when it strikes a boundary between different media through which it cannot pass is described as the reflection of light.

In a homogenous transparent medium light travels in a straight line and this is known as rectilinear propagation of light.

In order to get white light from the dispersed light the prisms are arranged as shown in the diagram. Recombination of the seven colours of the dispersed white light to get white light is known as recomposition of white light.