Class 8 physics Chapter 16 Refraction of Light and Our Eyes CBSE NCERT Science Book Solution
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Class 8 Ch light Book Basic science Solution
Download Science Mission class 8 Chapter 16 Light Solution Download 8th Refraction dispersion Book living science solution Download |
1. What is radius of plane mirror?
Ans: Infinity
2. What is angle of reflection for a ray falling normally on a plane mirror?
Ans: 0
3. Why do we use convex surface for side view mirror?
Ans: Convex mirror always form virtual, smaller and upright image of object for vide range.
4. Can a virtual image be photographed?
Ans: yes.
5. What is the power of a plane mirror?
Ans: 0 because focal length is at infinity
6. When the angle of incidence is 90 , what is the angle of refraction?
Ans: 0 degree
7. What is the value of refractive index of air?
Ans: 1. {The ratio of the sines of the angles of incidence and refraction will be the same if the medium is the
same.}
8. What is the magnification produced by a plane mirror?
Ans: Plane mirror cannot magnify image and has magnification 1 because height of image formed is equal to
that of object.
9. Define power. Give its S.I unit?
Ans: power of a lens is d ability of a lens to converge or diverge an incident rays of light. it is defined as the reciprocal of its focal length d = [1/f(m) ] Dioptre . Its S.I unit is Dioptre.
10. What is power of sun glass?
Ans: sun glasses do not converge or diverge rays of light hence have no power.
11. Between which two points related to a concave mirror should an object be placed to obtain on a screen an image twice the size of the object?
Ans. Between centre of curvature and the principal focus.
12. What are the two factors on which the lateral displacement of an emergent ray from a glass slab depends?
Ans. (i) Angle of incidence (ii) Thickness of glass slab
13.What is the minimum distance between an object and its real image in case of a concave mirror?
Ans. Zero, when object is at centre of curvature, its real image is also formed at the same point.
14. Why do we prefer a convex mirror as a rear- view mirror in vehicles?
Ans. It is because, it covers a wide rear field and forms small, erect and virtual image, close to the eye of the
driver of the vehicle.
15. What are rods and cone?
Ans: There are two types of receptors in the retina which are stimulated by light rays. They are rod cells and cone cells. Rod cells are stimulated by dim light and cone cells by intense light. This is because of the peculiarities in their pigments.
Rod cells contain the pigment rhodopsin and cone cells contain the pigment photopsin.
In man rod cells are few and cone cells are more in the yellow spot. Rod cells and cone cells are absent in the blind spot. Animals like cat and owl have more rod cells than man. So they have greater power of vision at night. Since the owl has no cone cells it cannot see in intense light.
Ans: Infinity
2. What is angle of reflection for a ray falling normally on a plane mirror?
Ans: 0
3. Why do we use convex surface for side view mirror?
Ans: Convex mirror always form virtual, smaller and upright image of object for vide range.
4. Can a virtual image be photographed?
Ans: yes.
5. What is the power of a plane mirror?
Ans: 0 because focal length is at infinity
6. When the angle of incidence is 90 , what is the angle of refraction?
Ans: 0 degree
7. What is the value of refractive index of air?
Ans: 1. {The ratio of the sines of the angles of incidence and refraction will be the same if the medium is the
same.}
8. What is the magnification produced by a plane mirror?
Ans: Plane mirror cannot magnify image and has magnification 1 because height of image formed is equal to
that of object.
9. Define power. Give its S.I unit?
Ans: power of a lens is d ability of a lens to converge or diverge an incident rays of light. it is defined as the reciprocal of its focal length d = [1/f(m) ] Dioptre . Its S.I unit is Dioptre.
10. What is power of sun glass?
Ans: sun glasses do not converge or diverge rays of light hence have no power.
11. Between which two points related to a concave mirror should an object be placed to obtain on a screen an image twice the size of the object?
Ans. Between centre of curvature and the principal focus.
12. What are the two factors on which the lateral displacement of an emergent ray from a glass slab depends?
Ans. (i) Angle of incidence (ii) Thickness of glass slab
13.What is the minimum distance between an object and its real image in case of a concave mirror?
Ans. Zero, when object is at centre of curvature, its real image is also formed at the same point.
14. Why do we prefer a convex mirror as a rear- view mirror in vehicles?
Ans. It is because, it covers a wide rear field and forms small, erect and virtual image, close to the eye of the
driver of the vehicle.
15. What are rods and cone?
Ans: There are two types of receptors in the retina which are stimulated by light rays. They are rod cells and cone cells. Rod cells are stimulated by dim light and cone cells by intense light. This is because of the peculiarities in their pigments.
Rod cells contain the pigment rhodopsin and cone cells contain the pigment photopsin.
In man rod cells are few and cone cells are more in the yellow spot. Rod cells and cone cells are absent in the blind spot. Animals like cat and owl have more rod cells than man. So they have greater power of vision at night. Since the owl has no cone cells it cannot see in intense light.
16. Q. A book is placed between two mirrors that are at right angles to each other. One of the images formed does not show lateral inversion. Where is this image formed and why is it not laterally inverted?
Ans: One of the images formed at the edge where mirror meet. This image is formed by rays that get reflected twice. As a result this image is not laterally inverted. |
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