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# Test: Ray Optics And Optical (CBSE Level With Solutions)

## 30 Questions MCQ Test Physics Class 12 | Test: Ray Optics And Optical (CBSE Level With Solutions)

Description
This mock test of Test: Ray Optics And Optical (CBSE Level With Solutions) for Class 12 helps you for every Class 12 entrance exam. This contains 30 Multiple Choice Questions for Class 12 Test: Ray Optics And Optical (CBSE Level With Solutions) (mcq) to study with solutions a complete question bank. The solved questions answers in this Test: Ray Optics And Optical (CBSE Level With Solutions) quiz give you a good mix of easy questions and tough questions. Class 12 students definitely take this Test: Ray Optics And Optical (CBSE Level With Solutions) exercise for a better result in the exam. You can find other Test: Ray Optics And Optical (CBSE Level With Solutions) extra questions, long questions & short questions for Class 12 on EduRev as well by searching above.
QUESTION: 1

### Light rays from a point object

Solution:

Light from each point on a luminous object travels outward in all directions in straight lines. Light travels at very high speeds, but is not instantaneously everywhere. Light from a point object travels indefinitely until it collides with matter in its path to be partially absorbed and reflected.

QUESTION: 2

Solution:
QUESTION: 3

### A lens of power + 2.0 D is placed in contact with another lens of power – 1.0 D. The combination will behave like

Solution:

P=P1​+P2​=+2−1=+1 dioptre, lens behaves as convergent
F=1​/P=1/1​=1m=100cm

QUESTION: 4

A short pulse of white light is incident from air to a glass slab at normal incidence. After travelling through the slab, the first colour to emerge is

Solution:
QUESTION: 5

According to Cartesian sign convention.

Solution:
QUESTION: 6

At the minimum deviation Dm, the refracted ray inside the prism

Solution:
QUESTION: 7

An observer looks at a tree of height 15 metre with a telescope of magnifying power 10. To him, the tree appears

Solution:

Magnification of a telescope is given by:
M= θio​ ​​
10= (h/di)/(h/do​) ​​
10= do​​/di​
Distance of image, di​=do​​/10

QUESTION: 8

Magnifying power of a compound microscope is high if

Solution:

Magnifying power of a compound- microscope is given by m=− (l​D​/f0​fe​)
where, l is length of tube
D is least distance of clear vision
f0​ is focal length of objective
fe​ is focal length of eyepiece
So, clearly, it can be seen that focal length of objective and eyepiece needs to be decreased so that magnifying power increases.

QUESTION: 9

According to Cartesian sign convention the heights measured

Solution:
QUESTION: 10

The bluish color predominates in a clear sky,

Solution:
QUESTION: 11

The magnifying power of the telescope can be increased by

Solution:
QUESTION: 12

A lamp and a screen are set up 100 cm apart and a convex lens is placed between them. The two positions of the lens forming real images on the screen are 40 cm apart. What is the focal length of the lens ?

Solution:

L1L2=40cm and O I=100cm
Therefore, x+40+x=100 or x=30cm
For lens at L1, we have
U=-30cm and v=+70
Thus,
(1/v)-(1/u)=1/f
Or, 1/f=(1/70) - (1/-30)
Or, f=+21cm

QUESTION: 13

The magnifying power of telescope is high if

Solution:
QUESTION: 14

Refraction is

Solution:
QUESTION: 15

Accommodation of the human eye is

Solution:
QUESTION: 16

The largest telescope in the world has a reflector with an aperture of 200 inches in order to achieve

Solution:
QUESTION: 17

A convex lens forms a real image of an object on a screen; the magnification of the image being 3/2. The object and the screen are kept fixed and the lens is moved through a distance of 16 cm when a sharp image is again formed on the screen; the magnification now being 2/3. What is the focal length of the lens?

Solution:
QUESTION: 18

A plano-convex lens, when silvered on the plane side, behaves like a concave mirror of focal length 30 cm. When it is silvered on the convex side, it behaves like a concave mirror of focal length 10 cm. The refractive index of the material of the lens is

Solution:

Given: A plano-convex lens when silvered on the plane side behaves like a concave mirror of focal length 60cm. However, when silvered on the convex side, it behaves like a concave mirror of focal length 20cm.
To find the refractive index of the lens
We know,
1/F​=(2/f​)+(1/fm)​​............(i), where
When plane surface is silvered it becomes concave mirror of focal length 60cm,
and fm​=∞
So the eqn(i) becomes,
1/60​=(2/f​)+(1/∞)​
⟹f=120cm
When convex side is silvered it becomes concave mirror of focal length 10cm,
and fm​=R/2​
So the eqn(i) becomes,
1/20​=2/f​+2/R
​⟹2/R=(1/20​)−(2/f)​
⟹2/R​=(1/20)​−(2/120)
​⟹2/R=(6−2​/120)
⟹R=60cm
Now using the focal length formula of the plano-convex lens, we get
1/f​=(μ−1)×1/R
⟹1/120=(μ−1)×1/60
​⟹μ−1=(60/120)
​⟹μ=(1/2)​+1
⟹μ=1.5
is the refractive index of the lens.

QUESTION: 19

For a rectangular slab, refraction takes place at

Solution:
QUESTION: 20

Farsighted or hypermetropic eye can be corrected by

Solution:
QUESTION: 21

A Plano convex lens of curvature of 30 cm & R.I. 1.5, produces a real image of an object kept 90cm from it. The magnification is

Solution:
QUESTION: 22

How will the image formed by a convex lens be affected if the central portion of the lens is wrapped in a black paper

Solution:
QUESTION: 23

An object is placed at a distance of 10 cm from a co-axial combination of two lenses A and B in contact. The combination forms a real image three times the size of the object. If lens B is concave with a focal length of 30 cm, what is the nature and focal length of lens A ?

Solution: QUESTION: 24

A converging lens is used to form an image on a screen. When the upper half of the lens is covered by an opaque screen

Solution:

The only difference in covering any part of a lens is that the intensity of the image will reduce. Since the focal length is a function of curvature of the surfaces of the lens and covering a part does not change it, the image will be formed as usual.

QUESTION: 25

Total internal reflection can take place only if light is travelling from

Solution:
QUESTION: 26

An equi-convex thin lens (μ =1.5) of focal length in air as 30cm is sealed into an opening in one end of tank filled with water ((μ =1.33). At the end of the tank opposite the lens is a plane mirror, 80 cm distant from the lens. The position of the image formed by the lens-water-mirror system of a small object outside the tank on the lens axis and 90cm to the left of the lens will be

Solution:
QUESTION: 27

Optical fibre communication uses the principle of

Solution:
QUESTION: 28

According to Cartesian sign convention.

Solution:
QUESTION: 29

When an astronomical telescope is focused on a distant star, the distance of the eye piece from the objective is 60 cm. When focused on a distant flag post the eye piece must be drawn at 0.1cm. If the focal length of the eye piece is 5cm; what will be the distance of the pole from the objective? Assume that the eye is focused for infinity?

Solution:
QUESTION: 30

The objective of a telescope has a focal length of 1.2 m. It is used to view a 10.0 m tall tower 2 km away. What is the height of the image of the tower formed by the objective?

Solution: