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PHYSICS, M7 2024 HSC 2 MC

Which of the following provides evidence for the model of light proposed by Huygens?

  1. Emission spectra
  2. Diffraction of light
  3. Black body radiation
  4. The photoelectric effect
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\(B\)

Show Worked Solution
  • Huygens’s proposed that light was a wave and light waves spread out in all directions as spherical wave fronts from a point source. 
  • Therefore the diffraction of light provided evidence for Huygens model of light as diffraction is a wave phenomena.

\(\Rightarrow B\) 

PHYSICS, M7 2023 HSC 3 MC

A diagram representing a double slit experiment using light is shown.
  

Which of the following best represents the expected pattern on the screen?
 

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\(C\)

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  • Light waves diffract when they pass through a double slit and produce an interference pattern.
  • The central maximum will occur in the centre of the screen where the path difference is 0 and where the path lengths differ by integral wavelengths.

\(\Rightarrow C\)

PHYSICS, M7 EQ-Bank 26

The diagram shows a light source, slits and a translucent screen arranged for an experiment on light. Light and dark bands form on the screen. The light has a wavelength of 590 nm. The diagram is not to scale.
 

  1. Explain how any one of the dark bands forms on the screen.  (3 marks)
  1. The distance between the centres of the double slit is 0.15 mm, and the distance between the double slit and the screen is 0.75 m.
  2. Calculate the distance on the screen from the centre of the central maximum to the centre of a second-order bright band.  (3 marks)
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a.   Dark band formation:

  • When light arrives at the double slit, it undergoes diffraction.
  • The two slits act as sources of secondary wavefronts and light travels from both slits to the screen.
  • When light from one slit travels any odd multiple of `(lambda)/(2)` more than light from the other slit to the screen, it is out of phase and destructive interference occurs. Here waves superimpose and cancel each other out, creating dark bands.
  • For example, the dark bands either side of the central maximum form where light from one slit travels `(lambda)/(2)` further than light from the other slit.

b.   `0.0059  text{m}`

Show Worked Solution

a.  Dark band formation:

  • When light arrives at the double slit, it undergoes diffraction.
  • The two slits act as sources of secondary wavefronts and light travels from both slits to the screen.
  • When light from one slit travels any odd multiple of `(lambda)/(2)` more than light from the other slit to the screen, it is out of phase and destructive interference occurs. Here waves superimpose and cancel each other out, creating dark bands.
  • For example, the dark bands either side of the central maximum form where light from one slit travels `(lambda)/(2)` further than light from the other slit.

b.    Using  `d  sin theta=m lambda`

  `0.15 xx10^(-3)  sin theta` `=2xx590 xx10^(-9)`
  `sin theta` `=0.007867`

 

  • Using trigonometry, `tan theta=(d)/(0.75)`, where `theta` is the angular separation of the second order bright band from the central maximum and `d` is the distance between the centre of the central maximum and the centre of the second order bright band.
  • As the angle, `theta` is small, the approximation  `sin theta=tan theta`  is valid:
  •    \( \tan \theta \approx \dfrac{d}{0.75} \ \ \Rightarrow \ \ d=0.007867 \times 0.75 \approx 0.0059 \mathrm{~m} \)

PHYSICS M7 2022 HSC 27

A laser producing red light of wavelength 655 nm is directed onto double slits separated by a distance, `d=5.0 xx 10^{-5} \ text{m}`. A screen is placed behind the double slits.
 


 

  1. Newton proposed a model of light. Use a labelled sketch to show the pattern on the screen that would be expected from Newton's proposed model.   (2 marks)
     

     
  2. When the laser light is turned on, a series of vertical bright lines are seen on the screen.
     
 
  1. Calculate the angle, `\theta`, between the centre line and the bright line at `A`.   (3 marks)
  1. The laser is replaced with one producing green light of wavelength 520 nm.
  2. Explain the difference in the pattern that would be produced.   (2 marks)
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a.   
       

 
b.   `theta=1.50^@`

c.   Consider  `d sin theta = m lambda :`

  • `sin theta prop lambda`
  • Using light with a shorter wavelength decreases the angular separation of bright fringes.
  •  The bright lines will appear closer together.
Show Worked Solution
a.   
     

Mean mark part (a) 53%.

b.   Using  `d  sin  theta=mlambda:`

`5.0 xx10^(-5)  sin  theta` `=2 xx6.55xx10^(-7)`
   `sin  theta` `=(2 xx6.55xx10^(-7))/(5.0 xx10^(-5))`
   `theta` `=1.50^@`

 

c.   Consider  `d sin theta = m lambda :`

  • `sin theta prop lambda`
  • Using light with a shorter wavelength decreases the angular separation of bright fringes.
  • The bright lines will appear closer together.

PHYSICS, M7 2021 HSC 8 MC

Light from a point source is incident upon a circular metal disc, forming a shadow on a screen as shown. A bright spot is observed in the centre of the shadow.
 

The bright spot is caused by a combination of

  1. interference and refraction.
  2. refraction and polarisation.
  3. polarisation and diffraction.
  4. diffraction and interference.
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`D`

Show Worked Solution
  • Light diffracts around metal disc and constructive interference causes the bright spot.

`=>D`