ASSIGNMENT
CLASS –X
SUBJECT- SCIENCE
CHAPTER: LIGHT-REFLECTION AND REFRACTION
Q1
Q2
Q3
What is the difference between ray of light and beam of light?
What is the angle of reflection if a ray falls normally on a plane mirror?
What should be the position of the object when a concave mirror is used:
(i) as a shaving mirror
(ii) as a doctor’s mirror
Q4
Differentiate between virtual image of a concave mirror and of a convex mirror?
Q5
The angle between an incident ray and the mirror is 40o.
(i)
What is the angle of incidence?
(ii)
What is the angle of reflection?
(iii) What is the total angle turned by light?
Q6
Why a ray of light passing through the centre of curvature of a concave mirror gets reflected
along the same path?
The outer surface of a hollow sphere of aluminium of radius 50 cm is to be used as a mirror.
What will be the focal length of this mirror? Which type of spherical mirror will it provide?
Define refraction. What is the difference between rarer medium and denser medium?
How is the refractive index of an optical medium related to the speed of light in that
medium? What is the unit of refractive index?
What is the cause of refraction?
A ray of light strikes the glass slab at an angle of 55o. What is the angle of incidence?
Q7
Q8
Q9
Q10
Q11
Q12
Q14
If refractive indices of water and alcohol are 1.33 and 1.36.Which is optically denser
medium?
“The refractive index of carbon disulphide is 1.63”.What is the meaning of this statement in
relation to speed of light?
If a light ray IM is incident on the surface AB as shown, identify the correct emergent ray.
Q15
Q16
Q17
Name a point inside a lens through which the light passes undeviated.
State two effects caused by the refraction of light.
Define power of a lens. Give its S.I. unit.
Q13
Q18
Q19
Q20
Q21
Q22
Q23
Q24
A spherical mirror and a lens both have focal length -20 cm. What type of mirror and lens
are these?
What is the power of combination of lens?
Under what condition a lens when placed in a transparent liquid becomes invisible?
How should two converging lenses be placed so that a parallel beam becomes parallel after
passing through two lenses?
How can you distinguish between a plane mirror, a concave mirror and a convex mirror
without touching them?
Define Snell’s law of refraction.
What is the relationship between refractive index of two medium?
Q25 NUMERICAL PROBLEMS (SPHERICAL MIRROR)
(I)
Find the size ,nature and position of image formed when an object of size 1 cm is placed
at a distance of 15 cm from a concave mirror of focal length 10 cm.
(II)
An object 2 cm high placed at a distance of 16 cm from a concave mirror which
produces a real image 3 cm high.
a) Find the position of the image.
b) What is focal length of mirror?
(III)
(IV)
An object is placed at a distance of 15 cm from a convex mirror of focal length 30 cm.
Find the position and nature of image.
Size of image of an object by a mirror having a focal length of 20 cm is observed to be
reduced to 1/3 of its size. At what distance the object has been placed from the mirror?
What is the nature of image and the mirror?
( REFRACTIVE INDEX)
(I)
If the angle of incidence for a light ray in air be 45o and the angle of refraction (r) in
glass be 30o. find the refractive index.
(II)
If the refractive index of water for light going from air to water be 1.33, what will be the
refractive index for light going from water to air?
(III)
With respect to air the refractive indices of water and benzene are 1.33 and 1.50
respectively. Calculate the refractive index of benzene with respect to water.
(IV)
For the same angle of incidence of 45o, the angle of refraction in three transparent media
A, B and C are 25o, 30o and 35o respectively. In which medium is the speed of light
minimum and in which medium maximum?
(Lenses)
(I)
(II)
(III)
(IV)
The image of a candle flame formed by a lens is obtained on a screen placed on the other
side of the lens. If the image is three times the image of the flame and the distance
between lens and image is 80 cm, at what distance should the candle be placed from the
lens? What is the nature of image at a distance of 80 cm and the lens?
How far should an object be placed from a convex lens of focal length 20 cm to obtain
its image at a distance of 30 cm from the lens? What will be the height of image if the
object is 6 cm tall?
An object 60 cm from a lens gives a virtual image at a distance of 20 cm in front of the
lens. What is the focal length of the lens? Is the lens converging or diverging?
A concave lens has focal length of 15 cm. At what distance should the object from the
lens be placed so that it forms an image at 10 cm from the lens? Also, find the
magnification produced by the lens.
(V)
A real image,4/5 size of the object is formed 18 cm from lens. Calculate the focal length
of the lens.
(POWER OF A LENS)
(i)
(ii)
The power of a lens is +2.5 D. What kind of lens it is and what is its focal length?
One student uses a lens of focal length 50 cm and another of -50 cm . What is the nature
of lens and its power used by each of them?