Chapter 9 Electromagnetic spectrum

Question 1

What is a wave?

Answer 1

A periodic oscillation that transfers energy from one place to another.

Question 2

What is a longitudinal wave? Give an example.

Answer 2

Oscillations are parallel to the direction of travel; e.g. sound waves.

Question 3

What is a transverse wave? Give an example.

Answer 3

Oscillations are perpendicular to the direction of travel; e.g. ocean waves.

Question 4

State the wave equation.

Answer 4

v = fλ

Question 5

What did Hans Ørsted discover in 1820?

Answer 5

A current-carrying wire produces a magnetic field.

Question 6

What did Michael Faraday show in the 1830s?

Answer 6

Changing magnetic fields produce electric fields.

Question 7

What was James Clerk Maxwell’s contribution in 1861?

Answer 7

Developed Maxwell’s equations showing light is electromagnetic radiation. Using 4 mathematical equations. He unified the electricity and magnetism.

Question 8

What did Heinrich Hertz demonstrate in the 1880s?

Answer 8

The existence of radio waves, which behave like light. ie traveling at the speed of light, being reflected, refracted, and polarized, and creating interference patterns that allowed him to measure their wavelength

Question 9

Write the wave equation for light.

Answer 9

c = fλ where c = 3.00 × 10^8 ms^-1

Question 10

How did Ole Rømer estimate the speed of light in the 1600s?

Answer 10

By observing the eclipses of Jupiter’s moon Io.

Question 11

Who provided a closer estimate in 1727 using starlight?

Answer 11

James Bradley.

Question 12

How did Hippolyte Fizeau measure the speed of light in 1849?

Answer 12

Using a toothed wheel and mirror 8 km away.

Question 13

How did Léon Foucault refine Fizeau’s method?

Answer 13

By using a rotating mirror.

Question 14

What value of the speed of light is used today?

Answer 14

c = 299,792,458 ms^-1

Question 15

What is the wavelength range of visible light?

Answer 15

390–780 nm.

Question 16

Which has greater penetrating power, short or long wavelength EMR?

Answer 16

Short wavelength EMR (e.g. X-rays, gamma rays).

Question 17

Why can’t AM radio waves escape Earth’s atmosphere?

Answer 17

Their long wavelength means very low penetrating power.