OP - Chromatic Aberrations - Week 11

Question 1

What wavelength/colour light would you prefer to design your optical system for?

Answer 1

Yellow light – about 485nm

Question 2

Does lens power differ with wavelength?

Answer 2

Yes. Short wavelength bends more (higher power)

I.e there’s a difference in refractive index and image point for different wavelengths

Question 3

When can you get BOTH transverse and longitudinal chromatic aberration?

Answer 3

For OFF-AXIS object points

Question 4

Difference between longitudinal and transverse aberrations?

Answer 4

Longitudinal - different colours focus on different planes (ie different focal lengths)

Transverse - different colours focus at different heights

Question 5

The moon.

Answer 5

If you are observing the moon through a telescope you’ll see that the edge of the moon is all weirdly coloured. Is due to transverse chromatic aberration

Question 6

Effect of aperture stop position on transverse aberration:

Answer 6

When the aperture stop is AT THE LENS: there is NO Transverse aberration

PPR is going through a nodal point (no refraction)

Question 7

Advantage of Galilean telescope?

Answer 7

Can cancel out longitudinal chromatic aberration due to the negative power of the eye lens

Question 8

Does a Keplerian telescope experience transverse chromatic aberration?

Answer 8

NOT FROM THE OBJECTIVE LENS. This is because the objective lens is the aperture stop. Pupil Ray goes through as a nodal ray, and no transverse Chrom aberration occurs

However, since the EYE LENS is NOT at the aperture stop, transverse aberration CAN occur from there