Human Eye and C...

A far sighted man cannot focus distinctly on objects closer than $$1m$$. What is the power of the lens that will permit him to read from a distance of $$40 \,cm$$.

What does the dispersion of light in a medium imply
i) Lights of different wavelength travel with different speeds in the medium.
ii) Light of any frequency will travel with the same speed in the medium
iii) The refractive index of the medium is different for different wavelength of light

Which phenomenon is responsible for the twinkling of stars?

For a normal eye, the cornea of eye provides as converging power of 40 D and the lens least converging power of the eye lens behind the cornea is 20 D. Using this information , the distance between the retina and the cornea – eye lens can be estimated to be:

For an equilateral prism if :
$$\angle { i } = angle\ of\ Incidence$$
$$\angle { e } = angle\ of\ Emergence$$
$$\angle { P } = angle\ of\ Prism$$
$$\angle { D } = angle\ of\ Deviation$$
then which one relation is correct :

After testing the eyes of a child, the optician has prescribed the following lenses for his spectacles:
left eye : $$+ 2\, D$$ Right eye: $$+ 2.25\, D$$
the child is suffering from the defective vision called:

A person suffering from an eyesight defect has a far point at $$40\ cm$$ and a near the point at $$25\ cm$$. The person uses a lens to see far away object. Find the near point of the person while wearing this lens.

Aperson suffering from defective vision can see objects clearly only beyond 100 cm from the eye. Find the power of lens required so that he can see clearly the object placed at a distance of distinct vision (D=25 cm)

The intensity of scattered light

A far sighted person can see object beyond 71 cm clearly if separation between glasses and eye lens is 2 cm, then find focal length of glass?