Practical investigation 2.2 Diffraction through a single slit 1. - - PowerPoint PPT Presentation

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Nov 12, 2023 450 likes •599 views

Practical investigation 2.2 Diffraction through a single slit 1. Investigative question What is the relationship between the width of a single slit and the diffraction pattern observed through the single slit? Method Hold a glass

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Practical investigation 2.2 Diffraction through a single slit

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1. Investigative question

What is the relationship between the width of a single slit and the diffraction pattern observed through the single slit?

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Method

Hold a glass slide with a narrow vertical slit

close to your eye and observe the light source through the slit. The slit and filament have to be in the same vertical plane.

Look through slits of different widths and

compare your observations.

Repeat with light of different colours.
Sketch and describe the single slit diffraction

pattern you observe in words.

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VARIABLE INDEPENDENT, DEPENDENT OR CONTROLLED REASON

Slit width Degree of diffraction Wavelength Colour of light

INDEPENDENT

Changed by the researcher

DEPENDENT

Measured by the researcher

CONTROLLED CONTROLLED

Controlled by the researcher Controlled by the researcher

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RESULTS:

Wider slit Narrower slit

The narrower the single slit, the more diffraction takes place.

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1.1 What causes the filament to look wider than it actually is?

The light undergoes diffraction.

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1.2 What causes the dark lines to the sides of the central bright line?

Destructive interference of light

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1.3 Which principle explains the observations?

Huygens’ principle

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2. Filters of different colours are placed in front of the

bulb. 2.1 Which colour shows the broadest central bright band?

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2.2 Give a reason for the difference in widths of the central band.

Longer wavelength → more diffraction → wider central band. Red light has the longest wavelength.

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2.3 How do the patterns for different colours compare further?

Alternating bright and dark bands

n either side of the central bright

band. White light  colours of spectrum; monochromatic light  only the colour of the light.

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3. Look at the bulb through slits of different widths.

What is the influence of slit widths on the pattern?

Wider slit width  less diffraction  narrower central band

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4. Is the diffraction of light similar to that of waves on

water?

YES

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5. What conclusion can you draw about the nature of

light?