Rajasthan Board Class 10 Science Chapter 9 Solution Light RBSE Class 10 Science Solution for Chapter 9
Objective type questions
1) Which mirror will show a wide area view
a) Plane mirror
b) Convex mirror
c) Concave mirror
d) Parabolic mirror
Ans-b) convex mirror
2) Speed of light will be maximum in
a) Water
b) Glass
c) Vacuum
d) Glycerin
Ans-c) vaccum
3) A coin at the bottom of a water tank appears to be raise because of the phenomenon of
a) Refraction
b) Reflection
c) Total internal reflection
d) Non of these
Ans- a) Refraction
4) If focal length of a mirror is + 60cm then the mirror is a
a) Concave mirror
b) Parabolic mirror
c) plane mirror
d) Convex mirror
Ans- d) convex mirror
5) Focal length of a plane mirror is
a) 0
b) 1
c) Infinity
d) None of these
Ans- c) infinity
6) Image in a convex mirror will always be
a) Real and upright
b) Real and inverted
c) Virtual and inverted
d) Virtual and upright
Ans- d) virtual and upright
7) The power of a lens is + 2diopter. What will be its focal length?
a) 2m
b) 1m
c) 0.5m
d) 0.2m
Ans- c) 0.5
8) In hypermetropia a person
a) Can see nearby objects
b) Can see far objects clearly
c) Neither nearby objects nor far objects are clearly visible
d) None of these
Ans- b) can see far objects clearly
9) To get a real image of the same size of objects, where shall the object where shall the object be placed before a convex lens of focal length 15cm?
a) 30cm
b) 15cm
c) 60cm
d) None of these
Ans-a) 30 cm
10) An object is placed at infinity with respect to a concave lens of focal length 20cm.distance of virtual images from lens will be
a) 10cm
b) 15cm
c) 20cm
d) At infinity
Ans- c) 20 cm
Very short type questions.
(1.) When an object absorbs all clours of light then which colour of the object will be seen by us?
Ans- black colour
(2.) To see our full image in a plane mirror what should be the lowest highest of the mirror?
Ans- equal to one half of your height
(3.) A light ray is incident on a plane mirror at an angle of 30, what will be the angle between the reflected and incident ray?
Ans- the angle between the of reflected ray is 60 degrees with the mirror surface.
(4.) Write two uses of a convex mirror.
Ans- it is used as side mirror in car, vehicle
It is also used in the magnifying glsss.
(5.) Write two uses of concave mirror.
Ans- it is used as solar surface.
Used in shaving mirrors.
(6.) Write mirror formula.
Ans- 1/v=1/u= 1/f
(7.) Write the relation between radius of curvature and focal length of a spherical mirror.
Ans- the focal length of the speherical mirror it then approximately half its radius of curvature.
(8.) Give the magnification formula.
Ans- M= v/u
(9.) Give snell’s law.
Ans- the angle of incident I and the angle of refraction r remains constant this is the snell’s law.
(10.) Write lens formula.
Ans—1/v-1/u= 1/f
(11.) What is the unit of power of lens?
Ans- dipotre is the unit.
(12.) In which condition a person with myopia cannot clearly see the object?
Ans-when the increase in the curvature of eye lens, then object can not see clearly.
(13.) Which defect of eye can be rectified with the help of a convex lens of appropriate power.
Ans- hyperpobia
(14.) What is cataract?
Ans- the eye starts reflecting light because of the reduction in transperancy and the object is not clearly visisble to eye this defect is known as Cataract.
(15.) What will be the nature of our image in a shaving mirror?
Ans- shaving mirror gives enlarge image.
Short type questions.
(1.) What do you mean by the regular reflection and diffused reflection?
Ans- when the energy is reflected from a plane surface is called regular reflection. In this reflection specific direction is same.
When the energy is reflected from the rough surface then it its called as diffused reflection. In this reflection the directions are different.
(2.) Explain the Cartesian sign convections for speherical mirrors.
Ans- this disease is starts with aging the transparency and flexibility of eye lens reduces, the eye starts reflecting light because of this reduction in transparency and the object is not clearly visible to such an eye this defect is known as Cataract. Now a days the artificial lens are used to replace the eye lens. The speherical mirrors are also used to correct the this defect.
(3.) Discuss the refraction of light and write the laws of refraction.
Ans- refraction is the change in direction of a wave passing from one medium to another or from a gradual change in the medium. Is known as refraction.
rules of refraction-
a) Incident ray, refracted ray and the perpendicular on the plane of refraction are in the same plane .
b) For refraction , refracting medium the ratio of sine of angle of includence I and sine of angle of refraction r is constant.
(4.) What are the different types of convex lenses and concave lenses.
Ans – convex lenses – there are three types of convex lenses
a) Plano- convex lenses b) double convex lenses and c) concave –convex lenses
Concave lenses –there are two types of lenses a) biconcave lenses and b) plano concave lenses.
(5.) Define principal focus and optical centre of a speherical lens.
Ans- principal focus – incident rays parallel to the principal axis refract from the lens and converge at a point known as principal focus.
Optical centre- it is the point of a lense is a point on the principal axis of the lens of that ray of light passing through is goes undiviated.
(6.) What is the power of accommodation of an eye and that is the range of the vision?
Ans- the power of accommodation is the ability of the eye lenses to focuses near and far objects clearly on the retina by adjusting its focal length. The power of accommodation is limited. generally the human eye can see an object clearly form ranges 25cm.
(7.) What do you mean by presbyopia and astigmatism?
Ans- presbyopia- the problem of eye in which person cannot see nearby as wel as distance objects clearly is known as presbyipia and it generally occur with age.
Astigmatism- it is because of irregular curvature of the cornea and people of all ages can be affected by this problem . a person with astigmatism cannot see clearly see horizontal lines and vertical lines at the same distance simultaneously.
(8.) What is hypermetropia? How this defect is corrected?
Ans- Hypermetaropia- it is also known as long sightdeness or far sightednesss. A person suffering from this is able to see distance objects clearly but can ot see near objects they objects are visible but not clear
To correct this defect of long sighedness a convex lens of appropriate power is placed before the eye.
(9.) What do you mean by myopia ? how is is corrected ?
Ans- it is also known as short sighedness or near sightedness. A person suffering from myopia can see the nearby objects clearly but distance objects are not very clear or distinct. On of the main reason for this defect increases is the ncreases in the curvature of eye lens.
To correct the defects of this concave lens of appropriate object is placed before the eye. Now a days laser technique is used to correct this defat.
(10.) What is power of lense?
Ans- reciprocal of the focal length of a lens is known as the power of the lens. When the light rays are incident on a concave lens then depending upon its focal length diverse the rays more and rays will bend more. The capacity of diverging or converging is inverse to the focal length .
Formula is P= 1/f
If f is in meter then P is in Diopter. Power of a convex lens is positive and power of a concave lens is negative.