λ × f = c — Practice Quiz

Question 1

Yellow sodium light has λ = 589 nm in vacuum. Its frequency is:

Accepted Answer

≈ 5.1 × 10¹⁴ Hz

Answer

≈ 5.1 × 10¹² Hz

Answer

≈ 1.96 × 10⁸ Hz

Answer

≈ 5.1 × 10¹⁶ Hz

Question 2

A wave of λ = 600 nm in vacuum enters glass (n = 1.5). Its wavelength inside the glass is:

Accepted Answer

400 nm

Answer

900 nm

Answer

600 nm

Answer

300 nm

Question 3

The energy of a 620 nm photon in eV is approximately:

Accepted Answer

2 eV

Answer

1 eV

Answer

5 eV

Answer

0.5 eV

Question 4

An EM wave has period 5 × 10⁻⁹ s. Its wavelength is:

Accepted Answer

1.5 m

Answer

0.15 m

Answer

15 m

Answer

0.015 m

Question 5

When light passes from vacuum into a medium of index n, which is true?

Accepted Answer

λ changes by factor 1/n

Answer

f changes

Answer

λ changes by factor n

Answer

v stays at c