Light Test

Result

Light Test - 28

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Weekly Quiz Competition

Question 1
1 / -0

A person has a $$18$$cm wide face and his two eyes are separated by 8 cm.Find the minimum width of a mirror required for the person to view is face laterally is

A
$$9$$cm

B
$$4$$cm

C
$$5$$cm

D
$$13$$cm

Solution

For minimum width -
i). Center of face and mirror must lie in perpendicular bisector of the line joining two eyes.
ii). Left eye must see right end point of face at the end of the mirror.
iii). Night eye must see left end point of face at then end of the mirror.
Now let,
$$F_1,F_2$$ end points of face width $$11E_1,E_2$$ two eyes $$11C-$$ center of face.
$$m_1.m_2-$$ mirror end points
$$m_1,m_2-$$ projection of $$m_1m_2$$ on line joining two eyes.
Now, line joining two eyes should look like -
$$F_1--E_1---m_1-C---m_2----E_2---F_2$$
Due to symmetry,
$$\Rightarrow F_1E_2=E_1F_2=13cm$$
Also, $$m_1,m_2$$ must be midpoint of $$F_1E_2$$ and $$E_1F_2$$ respectively.
So, $$E_1m_2=m_1E_2=\dfrac{13}{2}=6.5$$
$$E_1m_2=6.5$$
$$\Rightarrow E_1C+Cm_2=6.5$$
$$4+Cm_2=6,5$$
$$Cm_2=2.5$$
similarly $$m_1C=2.5$$
$$\Rightarrow m_1m_2=m_1C_1C_2=5cm=$$ mirror width.
Hence, the answer is $$5cm.$$
Question 2
1 / -0

The image of an object formed by a device is always virtual and small. The device may be

A
A glass plate

B
A concave mirror

C
A convex lens

D
A concave lens

Solution

Concave lenses always produce images that are upright, virtual, reduced in size, and located on the object's side of the lens.
Therefore, the image of an object formed by a concave lens is always virtual and small.
Question 3
1 / -0

Which type of an image is formed by a plane mirror?

A
Real & inverted

B
Real & erect

C
Virtual & erect

D
Virtual & inverted

Solution

The image that is formed by a plane mirror will be virtual, upright, same size and inverted

The object distance and the image distance will be equal.

Thus, the image formed by a plane mirror is virtual and inverted.
Question 4
1 / -0

The diameter of the sun subtends an angle of $$ 0.5^0 $$ at the surface of the earth. A converging lens of focal length $$100 \ cm$$ is used to provide an image of the sun on a screen. The diameter ( in mm) of the image formed is nearly

A
$$1$$

B
$$3$$

C
$$5$$

D
$$8.7$$
Question 5
1 / -0

The image formed by a convex mirror of a real object is

A
virtual and erect

B
virtual and inverted

C
real and erect

D
real and inverted

Solution

The image formed by a convex mirror of a real object is virtual and erect.
Question 6
1 / -0

Which diagram best shows the reflection of light?

A

B

C

D

Solution
Question 7
1 / -0

An object is at a distance of $$0.5$$ m in front of a plane mirror. The distance between the object and the image is

A
$$0.5 m$$

B
$$1 m$$

C
$$0.25 m$$

D
$$1.5 m$$

Solution

Hint:- In case of a plane mirror object distance is equal to image distance

Calculations:-
Here, the object distance = $$0.5\ m$$
Thus, the image distance = $$0.5\ m$$
The distance between the object and the image is $$0.5+0.5 = 1\ m$$
Question 8
1 / -0

While capturing solar energy for commercial purposes we use

A
Parabolic mirrors

B
Plane mirrors

C
Convex mirrors

D
Concave mirrors
Question 9
1 / -0

In which of the following cases we cannot get a virtual image using a plane mirror ?

A

B

C

D

Solution
Question 10
1 / -0

The passenger side-view mirror on an automobile often has notation. "Objects seen in the mirror are closer than they appear". Is the image really farther away than the object?

A
Yes, the image is smaller and farther away than the object.

B
Yes, the image is larger and farther away than the object.

C
No, the image is larger and closer than the object.

D
No, the image is smaller and closer than object.

Solution

As side-view mirrors are made up of Convex mirrors and they form smaller images and they make images far away than the object. That's why the image is smaller and closer than the object.