Online Test — The Human Eye and the Colourful World
18 Questions • 15 min • Chapter MCQ
15:00
Question 1 of 18
easy
Most of the refraction of light entering the eye takes place at the
eye lens
cornea
retina
iris
Explanation: The curved transparent cornea provides most of the eye's refracting power.
Question 2 of 18
easy
The light-sensitive screen at the back of the eye is the
pupil
retina
cornea
iris
Explanation: The image forms on the retina, which sends signals to the brain.
Question 3 of 18
easy
The near point of a normal human eye is about
25 cm
15 cm
40 cm
1 m
Explanation: The least distance of distinct vision is about 25 cm.
Question 4 of 18
easy
The size of the pupil is adjusted by the
ciliary muscles
iris
cornea
optic nerve
Explanation: The iris widens or narrows the pupil to control light entry.
Question 5 of 18
easy
The ability of the eye to focus on objects at different distances is called
dispersion
power of accommodation
scattering
persistence of vision
Explanation: Ciliary muscles change the lens focal length — accommodation.
Question 6 of 18
medium
Persistence of vision lasts for about
1 s
1/2 s
2 s
1/16 s
Explanation: An image lingers on the retina for roughly 1/16 second.
Question 7 of 18
easy
A person with myopia cannot see clearly
near objects
distant objects
any object
coloured objects
Explanation: Myopia (near-sightedness) blurs distant objects.
Question 8 of 18
easy
Myopia is corrected by using a
convex lens
concave lens
cylindrical lens
plane mirror
Explanation: A concave lens of negative power moves the image onto the retina.
Question 9 of 18
easy
Hypermetropia is corrected by using a
prism
plane mirror
concave lens
convex lens
Explanation: A convex lens of positive power helps near vision.
Question 10 of 18
medium
The power of a concave lens of focal length 0.25 m is
+4 D
-4 D
+0.25 D
-0.25 D
Explanation: Concave lens: f = -0.25 m, P = 1/f = -4 D.
Question 11 of 18
medium
The power of a convex lens of focal length 50 cm is
+2 D
-2 D
+0.5 D
-0.5 D
Explanation: f = +0.5 m, P = 1/0.5 = +2 D.
Question 12 of 18
medium
The age-related defect caused by loss of accommodation is
myopia
hypermetropia
presbyopia
cataract
Explanation: Presbyopia is due to weakening ciliary muscles with age.
Question 13 of 18
medium
Cataract in the eye is corrected by
a concave lens
a convex lens
surgery
bi-focal lenses
Explanation: The clouded lens is surgically replaced by an artificial one.
Question 14 of 18
medium
The correct order of colours in the spectrum from least to most deviated is
Violet to Red
Red to Violet
Green to Blue
Yellow to Orange
Explanation: Red deviates least and violet most; order Red...Violet (VIBGYOR reversed).
Question 15 of 18
medium
White light can be recombined into white light using
a single prism
two identical inverted prisms
a concave lens
a plane mirror
Explanation: Newton used a second inverted prism to recombine the spectrum.
Question 16 of 18
medium
The sky appears blue because air molecules scatter
red light most
blue light most
all colours equally
green light most
Explanation: Shorter blue wavelengths scatter most, filling the sky with blue.
Question 17 of 18
medium
The reddish colour of the Sun at sunrise is due to
dispersion
scattering of blue light over a long path
total internal reflection
diffraction
Explanation: Over the long horizon path, blue scatters away leaving red.
Question 18 of 18
medium
Stars twinkle while planets do not, mainly because of
dispersion in stars
atmospheric refraction
scattering in raindrops
reflection from the Moon
Explanation: Changing atmospheric layers refract point-like star light variably.