1. Write Snell's law with the help of diagram and explaining the meaning of
the symbols used.
2. What is a thin lens? What is the difference in construction between a
convex and a concave lens?
3. Why is a convex lens called a converging lens and a concave tens, a
diverging lens?
4. How do you conclude that a ray of light incident towards the optical centre
of a thin lens is transmitted almost without any deviation?
5. The focal length of a convex lens is f. How does the size of the image
placed in front of it changes as the object is brought progressively closer to
the focus from a distance which is just greater than 2f?
6. Assuming the principal axis as the x-axis and the optical centre as the origin,
how will you determine the signs of the quantities u, v and f for a lens?
7. Draw a neat diagram of the human eye and indicate and its main parts
8. How does the eye control the amount of light entering it?
9. What is the blind spot of the eye?
10. Why can you not see an object clearly if it is placed very close to your eyes?
Answers
Explanation:
1. the second law of refraction of light is called as a snell's law that law is the ratio of sine of angle of incidence to the sign of the angle of refraction is a constant for the light of given colour and for the given pair of media is low is also known as snell's law of refraction , if is the angle of incidence and r is the angle of refraction then
sin I/sine=constant
2. thin lens is a lens of thickness(distance among the optical axis between between the two surface of lens)that is negligible compared to the radius of curvature of the lens surface is called thin lens
convex lens are thicker at middle rays of light that pass through the lens are spread out (they diverge) the concave lens is adverging lens. when when parallel rays pass through the concave lens the refracted ray diverge so that so that they appear to come upon a one-point called principal focus
3. the the convex lens converges the light rays of a parallel beam to a particular point after refraction through the lens .hence convex lens is called converging lens
a concave lens diverges the light rays of a parallel beam after refraction through it. Hence concave lens is called diverging lens
4. hence a Ray passing through optical centre of a thin glass go straight without any deviation or displacement the centre of a lens is comparatively flat that the other points of the this can be found in thin lens rather than thick lens
5.at the greater than pure of the image is smaller compared to the object .at 2f the image size is equal to the object size .when it comes closer than to EF the magnification increases
6.
u=negative
v=positive if the images is virtual and negative if the images real
f=positive if the lens is concave and negative if the lens is convex
8.
the iris is the ring of pigmented tissue surrounding the pupil that varies is in color .the iris opens and closes to control the amount of light entering the eye through the pupil. the pupil is the opening in the centre of Iris where light enters the eye
9. the blind spot of the eye is where the optic nerve and blood vessels live in the eyeball the optic nerve is connected to the brain it carries images to the brain.
10. if an object is placed very close to the eyes the light reflected from it does not fall on the retina it either falls in front of the retina or behind it or the blind spot. hence, we cannot see the object.the minimum distance for seeing the object clearly is 25 CM.
diagrams of 1 and 7th question is in next page
