Olympiad Science - Light
Exam Duration: 45 Mins Total Questions : 30
'x' is a surface that cannot produce clear images. What is 'X'?
- (a)
Rough surface
- (b)
Ideal surface
- (c)
Smooth surface
- (d)
Smooth but curved surface
When light is incident on a rough surface, irregular reflection takes place, hence the image formed is not clear.
With what is glass coated in order to convert it into a mirror?
- (a)
Silver
- (b)
Copper
- (c)
Aluminium
- (d)
Platinum
Glass is coated with silver
What makes objects visible?
- (a)
The absorption of light by objects
- (b)
The reflected light from the object
- (c)
The total internal reflection taking place in an object
- (d)
The refracted light from the object
An object is visible only when reflected light from the object reaches the retina of our eyes
What is the phenomenon of light bouncing back into the same medium called?
- (a)
Reflection
- (b)
Refraction
- (c)
Dispersion
- (d)
Splitting
The phenomenon of light in which, light is reflected or bounced back into the same medium is called reflection.
What is the perpendicular drawn at any point on a mirror called?
- (a)
Incident ray
- (b)
Reflected ray
- (c)
Normal
- (d)
Image
The perpendicular drawn to the reflecting surface of a mirror at the point of incidence is called 'normal: The point on the reflecting surface where the light ray is incident is called the point of incidence.
If the angle of incidence is 80°, what will be the angle of reflection?
- (a)
80°
- (b)
100°
- (c)
160°
- (d)
20°
The angle of incidence = the angle of reflection. So, the angle of reflection is 80°.
Which of the following is used by E.N.T. doctors?
- (a)
Convex mirror
- (b)
Convex lens
- (c)
Plane mirror
- (d)
Concave mirror
A concave mirror is used by E.N.T.doctors to get a magnified image of internal organs like ear, nose and throat.
When the angle between two plane mirrors is 60°, how many images will be formed by the mirrors?
- (a)
5
- (b)
6
- (c)
7
- (d)
8
If two plane mirrors are inclined at an
angle of 60°, then
n = \(\frac { 360 }{ 60 } \)- 1 = 5 Images are forme
If the angle of incidence is 50°, then calculate the angle between the incident ray and the reflected ray
- (a)
50°
- (b)
100°
- (c)
130°
- (d)
80°
In reflection of light, < i = 50° and < i =
< r = the angle between incident ray and
reflected ray = 50° + 50° = 100°
In our houses, which of the following is used for looking at ourselves?
- (a)
Convex mirror
- (b)
Concave mirror
- (c)
Convex lens
- (d)
Plane mirror
We use plane mirrors to see ourselves because the image formed by a plane mirror is virtual, erect and of the same size.
Which of the following statements is true?
- (a)
The angle of incidence is twice the angle of reflection.
- (b)
The incident ray, the reflected ray and the normal drawn at the point of incidence lie in the same plane.
- (c)
Some virtual images can be caught on the screen
- (d)
Some virtual images can be caught on the screen
When a light ray is reflected from the reflecting surface, the incident ray, the reflected ray and the normal lie in the same plane. The angle of incidence = The angle of reflection
What happens in lateral inversion?
- (a)
The right side of the object will be on the right side of the image
- (b)
The left side of the object will be on the left side of the image
- (c)
The top of the object will be the bottom of the object
- (d)
The right side of the object will be on the left side of the image.
The image formed by the plane mirror is laterally inverted i.e., the right side of the object appears on the left side of the image and left side of the object appears on the right side of the image
What is the nature of image formed on the retina of human eye of an object?
- (a)
Virtual and erect
- (b)
Virtual and inverted
- (c)
Real and erect
- (d)
Real and inverted
The human eye serves as a convex lens. It forms real, inverted and diminished image of an object
Identify the value of persistence of vision.
- (a)
1/10th of a second
- (b)
1/12th of a second
- (c)
1/16th of a second
- (d)
1/20th of a second
Persistence of vision is a phenomenon where the brain continues to sense the image even after the object has been removed. This lasts for 1/16th of a second
Which of the following is the requirement of nocturnal animals like owl and bat?
- (a)
Large cornea
- (b)
Large pupil
- (c)
Retina with large number of rods
- (d)
large number of rods
The nocturnal animals need more light to see at night. The large cornea and pupil allow more light to enter into their eyes. They also have retina with large number of rods.
Look at the given figure.
Find the angle between the incident ray and the reflected ray.
- (a)
60°
- (b)
90°
- (c)
80°
- (d)
40°
< i = 40° (given)
<i= <r=40°
The angle between the incident ray and
the reflected ray
=<i+<r
= 40° + 40° = 80°
The diagram shows the path of a light ray X, directed at a plane mirror.
Which of the following is the correct reflected ray?
- (a)
M
- (b)
N
- (c)
O
- (d)
P
We know that for a reflected ray, the angle that the incident ray makes with the one perpendicular to the surface is equal to the angle made by the reflected ray with this perpendicular line. N is the correct reflected ray of X.
For a given incident ray, the plane of the mirror makes an angle e with the incident ray, then the reflected ray is turned through 2 e .Which of the following is based on the above principle?
- (a)
Periscope
- (b)
Kaleidoscope
- (c)
Shaving mirrors
- (d)
Automobile headlights
In the case of a periscope, the given fact is used and is illustrated below.
An object placed 4 m from a plane mirror is shifted by 0.5 m away from the mirror. What is the distance between the object and its image
- (a)
4m
- (b)
3.5 m
- (c)
9 m
- (d)
5 m
Object distance after shifting the object
=4 m + 0.5 m = 4.5 m
For a plane mirror;
Object distance = Image distance = 4.5 m
Distance between the object and its image
= 4.5 + 4.5 = 9 m
There are 11 letters in the word EXAMINATION. How many letters of this word are not changed when the word is seen in a plane mirror
- (a)
11
- (b)
5
- (c)
8
- (d)
9
The letters that are not changed when the word is seen by reflection are: X, A, M, I, A, T,1,0 i.e.8 letters.
How is a rainbow formed?
- (a)
When raindrops absorb sunlight
- (b)
When raindrops reflect sunlight
- (c)
When raindrops disperse sunlight
- (d)
When raindrops diffract sunlight
The dispersion of sunlight is the splitting of white light into rays of seven different colours. Just after the rain, there are a large number of water drops in the air which act like small prisms. As the white sunlight enters these water drops, the constituents of white light of different colours are refracted by different amounts, and a band of seven colours called rainbow is formed.
Which of the following letters will be seen without any change in a plane mirror?
- (a)
S
- (b)
T
- (c)
L
- (d)
P
T is a laterally symmetrical object and hence its image in a plane mirror would be the same as itself
Which of the following is the characteristic of an ideal mirror?
- (a)
It absorbs all the amount of light incident on it.
- (b)
It refracts all the light
- (c)
It reflects all the light
- (d)
All of the above
An ideal mirror reflects all the light
A series of fast-moving still pictures can create an illusion of movement. Why?
- (a)
The eye can focus on very rapidly changing pictures
- (b)
The eye is quicker than the brain.
- (c)
The eye can separate two images only when the interval of separation between them is one-sixteenth of a second.
- (d)
The optical cortex can see through the rapidly moving images
A series of fast moving still pictures can create an illusion of movement as the eye can separate two images only when the interval of separation between them is one-sixteenth of a second. This happens due to a phenomenon called persistence of vision.
Which of the following prevents internal reflections of light inside the human eye?
- (a)
Iris
- (b)
Pupil
- (c)
Choroid
- (d)
Blind spot
The inner layer of the eye called the choroid is black. This prevents internal reflections of light inside the human eye
For a normal eye, in an adult, what is the least distance of distinct vision?
- (a)
5 to 8 cm
- (b)
10 to 15 cm
- (c)
20 to 25 cm
- (d)
30 to 35 cm
The point nearest to the eye at which an object is distinctly visible is called the near point of the eye. The distance of the near point of the eye is called the least distance of distinct vision. It varies with age. For an infant, it is 5 to 8 ern, for an adult, it is 20 to 25cm.
Identify the part of the human eye on which different images are formed?
- (a)
Iris
- (b)
Pupil
- (c)
Cornea
- (d)
Retina
Images are formed on the retina.
Identify the nature of the image formed by the eye lens of a human eye
- (a)
Real, upright and enlarged
- (b)
Real, upright and diminished
- (c)
Real, inverted and diminished
- (d)
Virtual, inverted and diminished
The image formed on the retina is real, inverted and diminished. The optic nerve transmits the inverted image to the brain which reads it as an erect image.
Which of the following occurs in persons suffering from myopia?
- (a)
The eye ball is shortened
- (b)
Ciliary muscles contract
- (c)
The eye ball elongates
- (d)
The retina expands
A person suffering from myopia has elongation of the eye ball. As such he cannot see distant objects clearly. A suitable concave lens can rectify the above defect, so that the image falls on the retina.
According to the laws of reflection, which of the following statements is correct?
- (a)
The angle of incidence is greater than the angle of reflection
- (b)
The angle of incidence is less than the angle of reflection
- (c)
The angle of incidence is equal to the angle of reflection
- (d)
The angle of incidence is not equal to the angle of reflection
According to the laws of reflection, the angle of incidence is always equal to the angle of reflection.