Human Eye
What is the range of vision of a normal human eye?
From infinity to about 25 cm
The defect of vision which cannot be corrected by using spectacles.
Cataract
Explain Tyndall Effect.
The scattering of light by particles in its path is called Tyndall Effect.
Name two effects produced by the atmospheric refraction.
Twinking of stars
Advanced sunrise and delayed sunsets
What do you understand by the term accomodation of human eye
The abilityu of an eye to focus the distant objects as well as the nearby objects on the retina by changing the focal length of its lens.
What type of lens is used to correct the defect myopia?
Concave lens
What is the colour of sunlight
A) Scattered by dust particles
B) Scatterd by the air molecules
a) White
b) Blue
State whether the following statement is true or false
'The planets twinkle at night due to atmospheric refraction of light.'
False statement
A person walking in a dark corridor enters into a brightly lit room
State the effect on the pupil of the eye and the amount of light entering the eye.
Pupil becomes smaller and the amount of light entering the eye is reduced.
What are the cause for the defect called hypermetropia.
1. Due to shortening of eye ball
2. Due to low converging power of eye lens
On factors the colour of the scattered light depends.
The colour of the scattered light depends on the size of the scattering particles in the atmosphere.
Why do stars seems higher than they actually are?
Due to the atmospheric refraction the star seems higher because as the air higher up in the sky is rare and thats near the Earth's surface is denser. So as the light from the stars comes down the denser air bends the light more.
Explain why, when it is getting dark at night, it is impossible to make out the colour of cars on the road.
The colour detecting cells of the retina of eye called 'cones' do not work well in dim light .
A person can read a book clearly only if he holds it at an arms length from him. Name the defect of vision:
a) if the person is an old man
b) if the person is a young man
(a) Presbyopia
b) Hypermetropia
Why does the sky appear dark to an astraunaut instead of blue?
There is no atmosphere containing air in the space to scatter sunlight.
Explain the formation of a rainbow
A rainbow forms when sunlight interacts with raindrops in a process involving refraction, dispersion, and internal reflection.
Nocturnal animals tend to have wide pupils and lot of rods in their retinas. Suggest reason for this.
Wide pupils allow more light to enter the eye during night ; Rod cells in the retina are sensitive to dim light and hence help in seeing properly at night.
Find the focal length of a lens of power,-2.0 D. What type of lens is this?
The power of this lens has a negative sign so this is a concave lens.
P =-2.0
F= -50cm
In an experiment to study the scattering of light by passing a beam of white lioght through a colloidal solution of sulphur in a transparent glass tank:
a) Which colour is observed from the front of the glass tank?
b) Which colour is observed from the sides of the glass tank?
a) Red
b) Blue
4 minutes