w2 Single Vision 1 – Refraction and Lens power

Question 1

Absorption Spectra:

Answer 1

Certain wavelengths absorbed → dark lines (Fraunhofer lines).
Each element has unique absorption “fingerprints.”

Question 2

Emission Spectra:

Answer 2

Heated gases emit specific wavelengths.
These match their absorption spectra.

Question 3

What happens as refractive index gets higher??

Answer 3

Higher n → more bending of light → thinner lens for same power
→ Crucial when dispensing high Rx specs.

Question 4

Positive Lenses (Convex)

Answer 4

Thick centre, thin edge

Correct hyperopia/presbyopia

Question 5

types of positive convex lenses

Answer 5

biconvex: + front and back
plano-convex: + front, plano back
convex meniscus: + front, - back

Question 6

Negative Lenses (Concave)

Answer 6

Thin centre, thick edge

Correct myopia

Question 7

types of negative concave lenses

Answer 7

bioconcave: - front and back
plano-concave: plano front, - back
concave meniscus: + front, - back

Question 8

thin lens power formula

Answer 8

F = F1 + F2
F 1 = power of front surface
F 2 = power of back surface