Light Test

Result

Light Test - 18

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Question 1
1 / -0

An optician, while testing the eyes of a patient, keeps a chart of letters $$3$$m behind the patient and asks her to see the letters on the image of chart formed in a plane mirror kept at distance $$2$$m in front of her. How far away is the chart seen by the patient?

A
$$3$$m

B
$$2$$m

C
$$6$$m

D
$$7$$m

Solution

For plane mirrors, the object distance (do) is equal to the image distance (di). That is, the image is the same distance behind the mirror as the object is in front of the mirror. If we stand a distance of 2 meters from a plane mirror, we must focus at a location 2 meters behind the mirror in order to view our image.
In this case, a chart of letters is kept 3 m behind the patient and is asked to see the letters on the image of chart formed in a plane mirror kept at distance 2m in front of her. Therefore, the total distance from the chart and the mirror is 3 m+2 m=5 m.
As the object distance and image distance are equal, the image is formed at a distance of 5 m behind the mirror. The patient is at a distance of 2m from the mirror.
Hence, the total distance covered in viewing the image of the letters on the cart is 5 m+2 m = 7 m.
Question 2
1 / -0

An insect is sitting in front of a plane mirror at a distance $$1$$$$\ m $$ from it.(a) Where is the image of the insect formed?(b) What is the distance between the insect and its image?

A
$$(a)$$ $$2$$ $$m$$ behind the mirror $$(b)$$ $$1$$$$m$$

B
$$(a)$$ $$2$$$$m$$ infront of the mirror $$(b)$$ $$1$$$$m$$

C
$$(a)$$ $$1$$$$m$$ infront of the mirror $$(b)$$ $$2$$$$m$$

D
$$(a)$$ $$1$$$$m$$ behind the mirror $$(b)$$ $$2$$$$m$$

Solution

For plane mirrors, the object distance (do) is equal to the image distance (di). That is, the image is the same distance behind the mirror as the object is in front of the mirror. If we stand a distance of 2 meters from a plane mirror, we must focus at a location 2 meters behind the mirror in order to view our image.
In this case, an insect is sitting in front of a plane mirror at a distance $$1$$$$m$$ from it.
Case (a):
As the object distance and image distance are equal, the image is formed at a distance of 1 m behind the mirror.
Case (b):
The image distance is 1 m and the object distance is 1 m. Hence, the total distance between the insect and its image is 2 m.
Question 3
1 / -0

In the arrangement shown in fig, the image of the extended object as seen by the observer is:

A
Real and inverted

B
Real and erect

C
Virtual and inverted

D
Virtual and erect

Solution

Clearly as shown in the figure, the rays that emerge from the top of an extended source get reflected twice to stay at the top and thus give an erect image.
Also, plane mirrors always form a virtual image. Hence even such a combination gives a virtual image.
Question 4
1 / -0

The phenomenon of rebounding and change in direction of light when it strikes the surface of a mirror is called ____________.

A
Refraction

B
Diffraction

C
Reflection

D
None of these

Solution

Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated.
Question 5
1 / -0

In a plane mirror the image is formed:

A
Behind the mirror

B
In front of mirror

C
Both A & B

D
None of these

Solution

Images formed by plane mirrors are virtual, upright, left-right reversed, behind the mirror with the same distance from the mirror as the object's distance, and the same size as the object.
Question 6
1 / -0

A real image :

A
cannot be captured on a screen

B
can be captured on a screen

C
can be captured only on a celluloid screen

D
none of the above

Solution

$$\textbf{Correct option: Option (B).}$$

$$\textbf{Explanation:}$$

$$\bullet$$A real image is the image formed when the rays of light actually intersect after reflection or refraction. Thus, it can be captured on a screen.

$$\textbf{Thus, option (B) is correct.}$$
Question 7
1 / -0

A virtual image :

A
cannot be caught on a screen

B
can be caught on a screen

C
can be caught on an eyepiece

D
is formed by a prism

Solution

$$\textbf{Correct option: Option (A).}$$

$$\textbf{Explanation:}$$

$$\bullet$$A virtual image is formed when light rays appear to meet after reflection or refraction and thus it cannot be captured on screen.

$$\textbf{Thus, option (A) is correct.}$$
Question 8
1 / -0

We can see the objects only when:

A
reflected light from the objects reaches our eyes

B
the objects absorb all the light

C
when the objects allow all the light to pass through them

D
none of the above

Solution

Objects can only be seen when light falls onto the object and is reflected back to our eyes to form an image on the retina.
Question 9
1 / -0

Convex mirrors are used as rear view mirrors in the motor vehicles because :

A
they reflect light better than the other mirrors

B
they produce images which are more clearer than those produced by others

C
they produce magnified images

D
they form images which are much smaller than the objects

Solution

Convex mirrors are used as rear-view mirrors in motor vehicles because they form virtual and erect images which are much smaller than the objects irrespective of the distances of the object. The convex mirror helps the driver to view large areas of the traffic behind him and he can easily detect the vehicle coming or running behind him.
Question 10
1 / -0

In which direction light travels?

A
Any random direction

B
In straight line

C
In curved path

D
None

Solution

Light is always travel in straight line. For example, when we try to see a burning candle with a bent pipe we can not see the light coming from candle which proves that light always travel in straight line.