5.6 Diffraction

Question 1

What is diffraction?

Answer 1

» Spreading of waves when they pass through a gap or by an edge

Question 2

Why are telescopes better to observe distant planets compared to the naked human eye?

Answer 2

» Have a wider gap
» Therfore less diffraction occurs

Question 3

How can diffraction be increased by altering the gap?

Answer 3

» Making the gap narrower

Question 4

How can the diffraction be increased by altering the wavelength?

Answer 4

» Increase the wavelength

Question 5

What 5 things are observed when light is diffracted by a single slit?

Answer 5

» Intensity is greatest at the central fringe
» The central fringe is twice as wide as each of the outer fringes
» Brightness of each fringe decreases with distance from the centre
» Outer fringes are the same width
» The outer fringes are much dimmer than the central fringe

Question 6

What 5 things are observed when light is diffracted by a single slit?

Answer 6

» Intensity is greatest at the central fringe
» The central fringe is twice as wide as each of the outer fringes
» Brightness of each fringe decreases with distance from the centre
» Outer fringes are the same width
» The outer fringes are much dimmer than the central fringe

Question 7

What is observed when using greater wavelength of monochromatic light in the single slit diffraction?

Answer 7

» The greater the wavelength, the wider the fringes

Question 8

What is the width of the central fringe in the single slit diffraction?

Answer 8

» W = lambda/ a x 2D
» Lambda = wavelength
» a = the width of the single slit
» D is the distance from the screen from the slit

Question 9

What happens as the angular position increases?

Answer 9

» Intensity decreases

Question 10

Explain the differences between white light and laser light diffraction?

Answer 10

» Laser - monochromatic pattern, white light non-monochromatic
» Laser - dark and light fringes, white light - multicolor fringes/spectra
» Laser doesn’t have white central fringe

Question 11

What happens to the width of the central maximum if you increase the slit width?

Answer 11

» Decreases diffraction central becomes narrower
» Intensity increases

Question 12

Why are the outer fringes dimmer then inner fringes in the young’s experiment?

Answer 12

» Because they are contained within the envelope of the single slit pattern and the single slit evenlop intensity gets less at the outer edges

Question 13

What would happen to the fringes if the slits-were made wider without chaging their centre-to-centre seperation?

Answer 13

» Less diffraction occurs
» More narrow