5.5 More about interference Flashcards

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1
Q

Why are double slits described as coherent sources ?

A

» Because they emit light waves of the same frequency with a constant phase difference

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2
Q

Why are slits, rather than 2 seperate light sources are used in the Young’s double slit experiment?

A

» They could not form an interference pattern
» As the 2 light sources emit light waves at random
» The points of cancellation and reinforcement would change at random

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3
Q

What is white light composed of?

A

» A continuous spectrum of colors - corresponding to a continuous range of wavelengths

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4
Q

Why does red light have a larger the fringe seperation then blue light?

A

» Red light has a longer wavelength
» According to : w = (lambda x D)/s
» Therefore the longer the wavelnegth of the light used, the greater the fringe seperation

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5
Q

What do vapour lamps and discharge tubes produce?

A

» Light with a dominant color
» Emit other wavelengths of light - but not as dominant
» Effectively are monochromatic sources of light

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6
Q

What type of light is produced from a filament lamp or from the sun?

A

» Composed of the colors of the spectrum and therefore covers a continous range of wavelengths

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7
Q

What type of light is produced from a laser?

A

» Highly monochromatic - a single wavelength is produced
» Almost perfectly parallel

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8
Q

Why is a laser used to demonstrate the double slit interference?

A

» Coherent source of light
» As the photons in the laser are in phase with each other when de-excitation happens

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9
Q

What are 4 precautions to take when working with lasers?

A

» Wear laser saftey goggles
» Display a warning sign
» Dont shine the laser at reflective surfaces

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10
Q

What are some things you may observe when using white light instead of monochromatic light?

A

» A wider maxima
» Less intense diffraction pattern
» A central white fringe
» Alternating bright fringes
» Red furthest, blue closest

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11
Q

How does the knowledge and understanding of any scientfic concept change over time?

A

» According to the experimental evidence gathered by the scientfic community

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12
Q

Why are the blue fringes closer then the red fringes in the fringe pattern of white light?

A

» As red fringes are more spaced out than the blue fringes
» Due to larger wavelengths

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13
Q

Describe the appearances of fringes from a monchromatic source of light?

A

» Monochromatic pattern - dark fringe, light fringe
» Equal sized fringes
» Equally spaced - fringe seperation is equal
» Can be either vertical or parallel - pay attention to the question

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14
Q

Explain why more fringes will be seen if each of the slits is made narrower, assuming that no other changes are made?

A

» More diffraction occurs
» More overlap
» More fringes - with the same width

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