Diffraction is the spreading out of waves after they pass through a narrow gap or around an obstruction.

When are diffraction effects most noticeable?

Diffraction effects are most noticeable when the wavelength of the wave and the width of the gap are similar in size.

How does the central maximum in a single slit diffraction pattern compare to the other bright fringes?

The central maximum is much wider and brighter than the other bright fringes, which get dimmer as the order increases.

Red light, which has the .......... wavelength of visible light, produces a diffraction pattern with .......... fringes.

Red light, which has the longest wavelength of visible light, produces a diffraction pattern with wider fringes.

What happens to a single slit diffraction pattern when the slit is made narrower?

The angle of diffraction increases The waves spread out more beyond the slit The intensity of the maxima decreases The width of the central maximum increases The spacing between fringes increases

Why is the central maximum white when white light is diffracted through a single slit, while the other maxima show spectra?

The central maximum is white because constructive interference from all the colours occurs at this point. At other maxima, each wavelength diffracts by a different amount, producing separate spectra .

True or False? Blue light diffracts more than red light because blue light has a longer wavelength.

False. Red light has the longer wavelength and diffracts more than blue light, which has a shorter wavelength and diffracts less.

Define a diffraction grating .

A diffraction grating is a piece of optical equipment consisting of a large number of very thin, equally spaced parallel slits carved into a glass plate, used to diffract light.

At the n th order maximum of a diffraction grating, the path difference between adjacent slits is equal to ..........

At the n th order maximum of a diffraction grating, the path difference between adjacent slits is equal to n*λ *.

State two applications of diffraction gratings.

Spectrometers, to analyse the composition or red shift of stars X-ray crystallography, to measure atomic spacing in crystals Monochromators, to select or excite specific wavelengths of light Selecting the optimum wavelength for use in optical fibres

True or False? A diffraction grating produces wider, less intense bright fringes than a double slit.

False. A diffraction grating produces a sharper pattern than a double slit — its bright fringes are narrower and brighter , with wider, darker regions in between.

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Diffraction (AQA A Level Physics): Flashcards

Exam code: 7408

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FrontSingle Slit Diffraction
Define diffraction.

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Cards in this collection (14)

Define diffraction.
Diffraction is the spreading out of waves after they pass through a narrow gap or around an obstruction.
When are diffraction effects most noticeable?
Diffraction effects are most noticeable when the wavelength of the wave and the width of the gap are similar in size.
How does the central maximum in a single slit diffraction pattern compare to the other bright fringes?
The central maximum is much wider and brighter than the other bright fringes, which get dimmer as the order increases.
Red light, which has the .......... wavelength of visible light, produces a diffraction pattern with .......... fringes.
Red light, which has the longest wavelength of visible light, produces a diffraction pattern with wider fringes.
What happens to a single slit diffraction pattern when the slit is made narrower?
- The angle of diffraction increases
- The waves spread out more beyond the slit
- The intensity of the maxima decreases
- The width of the central maximum increases
- The spacing between fringes increases
Why is the central maximum white when white light is diffracted through a single slit, while the other maxima show spectra?
The central maximum is white because constructive interference from all the colours occurs at this point. At other maxima, each wavelength diffracts by a different amount, producing separate spectra.
True or False?
Blue light diffracts more than red light because blue light has a longer wavelength.
False.
Red light has the longer wavelength and diffracts more than blue light, which has a shorter wavelength and diffracts less.
Define a diffraction grating.
A diffraction grating is a piece of optical equipment consisting of a large number of very thin, equally spaced parallel slits carved into a glass plate, used to diffract light.
State the diffraction grating equation and define each term.
$d \sin θ = n λ$
- n is the order of the maximum
- d is the distance between the slits on the grating (m)
- θ is the angle of diffraction of order n from the normal
- λ is the wavelength of the light (m)
How is the slit spacing, d, calculated from the number of lines per unit length, N?
$d = \frac{1}{N}$
If N is given in lines per mm, d is in mm. If N is given in lines per m, d is in m.
How is the highest order of maxima visible from a diffraction grating determined?
The maximum angle of diffraction is 90°, so sin θ = 1, giving:
$n = \frac{d}{λ}$
If this gives a decimal, it must be rounded down to find the highest order visible.
At the nth order maximum of a diffraction grating, the path difference between adjacent slits is equal to ..........
At the nth order maximum of a diffraction grating, the path difference between adjacent slits is equal to n*λ*.
State two applications of diffraction gratings.
- Spectrometers, to analyse the composition or red shift of stars
- X-ray crystallography, to measure atomic spacing in crystals
- Monochromators, to select or excite specific wavelengths of light
- Selecting the optimum wavelength for use in optical fibres
True or False?
A diffraction grating produces wider, less intense bright fringes than a double slit.
False.
A diffraction grating produces a sharper pattern than a double slit — its bright fringes are narrower and brighter, with wider, darker regions in between.

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