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Test: Ray Optics - 1

25 Questions MCQ Test NCERT Textbooks (Class 6 to Class 12) | Test: Ray Optics - 1

Description

Attempt Test: Ray Optics - 1 | 25 questions in 25 minutes | Mock test for Class 10 preparation | Free important questions MCQ to study NCERT Textbooks (Class 6 to Class 12) for Class 10 Exam | Download free PDF with solutions

QUESTION: 1

A mirror forms a virtual image of a real object.

A.
It must be a convex mirror.
B.
It must be a concave mirror.
C.
It must be a plane mirror.
D.
It may be any of the mirrors mentioned above.

Solution:

The image in a plane mirror forms virtual and erect image and appears to be as far behind the mirror as the object is in front of the mirror. A diverging lens or a convex mirror forms a virtual image.A virtual image is produced by a concave mirror when the object is placed inside the focal length of the mirror.

QUESTION: 2

The angle of incidence is the angle between

A.
the incident ray and the surface of the mirror
B.
the reflected ray and the surface of the mirror
C.
the normal to the surface and the incident ray
D.
the normal to the surface and the reflected ray

Solution:

QUESTION: 3

The angle of reflection is the angle between

A.
the incident ray and the surface of the mirror
B.
the reflected ray and the surface of the mirror
C.
the normal to the surface and the incident ray
D.
the normal to the surface and the reflected ray

Solution:

Angle of reflection is the angle between a reflected ray and the normal drawn at the point of incidence to a reflecting surface.

QUESTION: 4

An object is placed at the centre of curvature of a concave mirror. The distance between its image and the pole is

A.
equal to f
B.
between f and 2f
C.
equal to 2f
D.
greater than 2f

Solution:

When the object is placed at the center of curvature, the image is formed at the center of curvature and we know that the relation between radius of curvature and focal length is R= 2F ( R is used to show radius of curvature And F is the focal length ) if you will notice the its ray diagram then u could see that radius of curvature is always twice of Focal length.

QUESTION: 5

An object of size 2.0 cm is placed perpendicular to the principal axis of a concave mirror. The distance of the object from the mirror equals the radius of curvature. The size of the image will be

A.
0.5 cm
B.
1.5 cm
C.
1.0cm
D.
2.0 cm

Solution:

The size of the image will be 2.0 cm.
V=U(given)
m=-v/u
m= - 1
m=h`/h
-1=h`/2
h`=-2
h=2cm

QUESTION: 6

The magnification m of an image formed by a spherical mirror is negative. It means, the image is

A.
smaller than the object
B.
larger than the object
C.
erect
D.
inverted

Solution:

For spherical mirrors,

m = - v/u

‘m’ is negative when both ‘v’ and ‘u’ have negative values. That is both object and image are on the same side.

So, the correct option is d. The image is inverted, since, it is real.

QUESTION: 7

A point object is placed on the principal axis of a spherical mirror. The object-distance u is

A.
definitely negative
B.
definitely positive
C.
positive if the object is to the left of the centre of curvature
D.
positive if the object is to the right of the centre of curvature

Solution:

Option ( a) is the correct answer. As the object is always placed on the left side of the mirror and according to the sign convention, it has negative value for 'so axis.

Therefore, spherical mirrors have only one reflecting surface and it will be negative only.

QUESTION: 8

f = R/2 is valid

A.
for convex mirrors but not for concave mirrors
B.
for concave mirrors but not for convex mirrors
C.
for both convex and concave mirrors
D.
neither for convex mirrors nor for concave mirrors

Solution:

The relation f = R/2 is applicable only for mirrors. For lenses, you have to use the lens makers formula.

QUESTION: 9

A ray of light is incident on a concave mirror. If it is parallel to the principal axis, the reflected ray will

A.
pass through the focus
B.
pass through the centre of curvature
C.
pass through the pole
D.
retrace its path

Solution:

QUESTION: 10

If an incident ray passes through the centre of curvature of a spherical mirror, the reflected ray will

A.
pass through the pole
B.
pass through the focus
C.
retrace its path
D.
be parallel to the principal axis

Solution:

An incident ray which passes through the centre of curvature C of the mirror is reflected back along it's own path ( since it is normally incident on the mirror) .

QUESTION: 11

To get an image larger than the object, one can use

A.
a convex mirror but not a concave mirror
B.
a concave mirror but not a convex mirror
C.
either a convex mirror or a concave mirror
D.
a plane mirror

Solution:

A convex mirror never forms an image larger than the original object, whereas a concave mirror can form an image larger than the object between the centre of curvature and the point of focus.

QUESTION: 12

A ray of light travelling in air falls obliquely on the surface of a calm pond. It will

A.
go into the water without deviating from its path
B.
deviate away from the normal
C.
deviate towards the normal
D.
turn back on its original path

Solution:

The light ray bends towards the normal as it travels from a rarer medium of air to a denser medium of water, under goes refraction. Refraction is due to change in the speed of light as it enters from one transparent medium to another. The speed of light increases in rarer medium and decreases in denser medium.

QUESTION: 13

A ray of light goes from a medium of refractive index μ1 to a medium of refractive index μ2. Theangle of incidence is i and the angle of refraction is r. Then, sin i/sin r is equal to

A.
μ1
B.
μ2
C.
μ1/μ2
D.
μ2/μ1

Solution:

Refractive index, also called index of refraction, measure of the bending of a ray of light when passing from one medium into another. As per Snell's law and the given information ;

QUESTION: 14

A thin lens and a spherical mirror have a focal length of + 15 cm each.

A.
Both are convex.
B.
The lens is convex and the mirror is concave.
C.
The lens is concave and the mirror is convex.
D.
Both are concave.

Solution:

According to sign convention distances and points are given their positive or negative sign on the basis of direction of propagation of incident Ray and the focus of both convex mirror and lens are in the front of propagating incident Ray of light so it is taken as positive

QUESTION: 15

A convex lens

A.
is thicker at the middle than at the edges
B.
is thicker at the edges than at the middle
C.
has uniform thickness everywhere
D.
is called a diverging lens

Solution:

QUESTION: 16

A convex lens forms a virtual image when an object is placed at a distance of 18 cm from it. The focal length must be

A.
greater than 36 cm
B.
greater than 18 cm
C.
less than 36 cm
D.
less than 18 cm

Solution:

A virtual image of an object is formed by a convex lens only when the object is placed between the lens and the focus. Therefore, the focal length of the lens should be greater than the distance of the object from the lens.

QUESTION: 17

An object is placed before a convex lens. The image formed

A.
is always real
B.
may be real or virtual
C.
is always virtual
D.
is always erect

Solution:

QUESTION: 18

An object is placed before a concave lens. The image formed

A.
is always erect
B.
may be erect or inverted
C.
is always inverted
D.
is always real

Solution:

Because concave lens always produce an
Image which is always erect, diminished and virtual.

QUESTION: 19

A lens has a power of +0.5 D. It is

A.
a concave lens of focal length 5 m
B.
a convex lens of focal length 5 cm
C.
a convex lens of focal length 2 m
D.
a concave lens of focal length 2 m

Solution: P=1/f f=1/p. f=1/0.5 f = 2m

QUESTION: 20

A parallel beam of light falling on the eye gets focused on the retina because of refractions at

A.
the cornea
B.
the crystalline lens
C.
the vitreous humor
D.
various surfaces in the eye

Solution:

Most of the refraction for the light rays entering the eye occurs at the outer surface of the cornea.

QUESTION: 21

The combination responsible for admitting different amounts of light into the eye is

A.
ciliary muscles and crystalline lens
B.
ciliary muscles and pupil
C.
iris and pupil
D.
rods and cones

Solution:

QUESTION: 22

The muscles of the iris control the

A.
focal length of the eye-lens
B.
opening of the pupil
C.
shape of the crystalline lens
D.
optic nerve

Solution:

QUESTION: 23

When the eye is focused on an object very far away, the focal length of the eye-lens is

A.
maximum
B.
minimum
C.
equal to that of the crystalline lens
D.
half its maximum focal length

Solution:

QUESTION: 24

Other names for myopia are

A.
hyperopia and hypermetropia
B.
long-sightedness and hyperopia
C.
near-sightedness and presbyopia
D.
near-sightedness and short-sightedness

Solution:

QUESTION: 25

The inability among the elderly to see nearby objects clearly because of the weakening of the ciliary muscles is called

A.
far-sightedness
B.
near-sightedness
C.
presbyopia
D.
astignatism

Solution:

The inability among the elderly to see near objects clearly because of the weakening of the ciliary muscles is called presbyopia. The focusing power of the eye lens decreases with age.