Chapter 9b Spectroscopy

Question 1

What is spectroscopy?

Answer 1

The study of spectra produced when matter interacts with or emits electromagnetic radiation.

Question 2

Name two fields where spectroscopy is widely used.

Answer 2

Chemistry (to detect and characterise atoms and molecules) and astronomy.

Question 3

What is absorption sprectra

alos know as Fraunbhofer lines

Answer 3

Dark lines in the spectrum of sunlight caused by missing colours.

Question 4

What causes absorption sprectra

Answer 4

They are caused by gases in the Sun’s atmosphere absorbing specific wavelengths of light.

can also occur as light travels through gas clouds (neubla)

Question 5

How can absorption spectra identify elements?

Answer 5

Each element absorbs specific wavelengths unique to its atoms.

Question 6

What happens when atoms are excited and then return to the ground state?

Answer 6

They emit light of a specific colour, depending on the energy released.

Question 7

What is an emission spectrum?

Answer 7

A distinctive combination of colours produced by an element when heated or electrically excited.

Question 8

Why do fireworks produce different colours?

Answer 8

Different metals produce unique emission spectra (e.g., strontium = red, sodium = yellow, copper = green).

Question 9

What is a spectroscope?

Answer 9

A device combining a diffraction grating and telescope to view spectra of light.

Question 10

What is the difference between a spectroscope and a spectrometer?

Answer 10

A spectrometer has a graduated scale (or electronic system) to measure specific wavelengths.

your saw this machine at the uni

Question 11

Why do incandescent bulbs produce a continuous spectrum?

Answer 11

Their tungsten filament is heated, emitting light across a wide range of wavelengths.

Question 12

What type of spectrum do fluorescent lights produce?

Answer 12

A ‘spiky’ spectrum with discrete narrow bands.

Question 13

How do fluorescent lights work?

Answer 13

Fluorescent lights work by passing an electric current through a gas-filled tube containing mercury vapor. The current excites the mercury, which produces ultraviolet (UV) light. This UV light then strikes a phosphor coating on the inside of the tube, causing the coating to glow and emit visible light.

Question 14

What wavelengths are used to study hot stars, supernovae, and nuclear processes?

Answer 14

Ultraviolet, X-rays, and gamma rays.

Question 15

What is the approximate composition of the Sun?

Answer 15

71% hydrogen, 27% helium, and <2% other elements.

Question 16

What can the spectrum of a star reveal about its chemical composition?

Answer 16

The absorption and emission lines show which elements are present.

Question 17

How can a star’s surface temperature be determined from its spectrum?

Answer 17

Using Wien’s Law — the peak wavelength of emitted light is inversely proportional to temperature.

Question 18

How can a star’s density be determined from its spectrum?

Answer 18

By analysing the width of absorption lines — broader lines indicate higher density.

main sequence stars are more dense than red giants so have thick absorpt

Question 19

How can the motion of a star be measured from its light?

Answer 19

Through the Doppler effect — shifts in spectral lines reveal motion towards (blue shift) or away (red shift) from Earth.

Question 20

How does light reveal if a planet or moon has an atmosphere?

Answer 20

Missing wavelengths in reflected light show absorption by gases in the atmosphere.

Question 21

How do astrophysicists identify chemical composition in distant stars?

Answer 21

By matching spectral lines to known atomic emission/absorption patterns.