Flashcards in Turning points - Wave particle duality Deck (62)
TP Chapter 2 Q) Describe Newton's corpuscular theory of light
A) That light is made of corpsucles. Different colours are made of diffent size corpuscles.
TP Chapter 2 Q) Describe Huygens' theory of light
A) That light is made of waves. Wave behaviour can be described by drwaing geometrical wavefronts.
TP Chapter 2 Q) What would happen in refraction according to Newton?
A) Light would slow down when it enter's a material from air. This causes the change in direction in the material and due to light speeding up when it reenters air, explains it's change in direction when light emerges.
TP Chapter 2 Q) What would happen in refraction according to Huygen?
A) Light would speed up due to an unknown short range attractive force between the material and the corpuscle. This would increase the 'vertical' component of velocity but not horzontal - changing the directino of light. When light emerges the same force 'attracts' the light back - reducing the 'vertical' component of velocity.
TP Chapter 2 Q) State three reasons why Huygen's theory was not accepted
A) Newton's other theories were successful. Huygen's theory was based on longitudinal waves which could not explain polarisation. Huygen's theory could not explain sharp shadows.
TP Chapter 2 Q) Outline Young's double slit experiment
A) Light is shone through a single slit which the is shone through two narrow slits. Light then travels onto a screen to display an interference pattern.
TP Chapter 2 Q) State the equation for Young's double slit
A) w = λD/s
TP Chapter 2 Q) What did Huygens' theory predict for Young's double slit experiment
A) That an intereference pattern would occur with bright and dark fringes.
TP Chapter 2 Q) What did Newton's theory predict for Young's double slit experiment
A) That there would be two columns of light where the corpuscules went through the slits.
TP Chapter 2 Q) What does Young's double slit tell you about the nature of light?
A) That light is a wave.
TP Chapter 2 Q) Explain why more than two bright fringes are seen in Young's double slit experiment
A) Bright fringes are caused by constructive intereference. This occurs when there is a phase difference of 0, 360, 720 etc degrees. This is caused when there is a path difference of 0,1,2 etc wavelengths. This occurs due to the geometry of the slits and screen.
TP Chapter 2 Q) How did Fizeau measure the speed of light?
A) As constructive interference occurs when there is a path difference of an integer number of wavelengths. As the wavelength of ight is small it is highly likely that many fringes would occur on a screen.
TP Chapter 2 Q) Explain what was happening when Fizeau did not see light
A) Light shone through a gap, but by the time light had travelled and reflected back, the wheel had turned from a gap to a tooth. The light was blocked out by the tooth in the cog.
TP Chapter 2 Q) Explain what was happening when Fizeau did see light
A) The wheel had turned to the next gap by the time light had travelled to the mirror and reflected.
TP Chapter 2 Q) State the equation for Fizeau's experiment
A) c = 4dnf
TP Chapter 2 Q) Why was Fizeau's measurement of the speed of light in water significant?
A) Newton predicted light travelled faster in water, where as Huygen predicted light travelled slower in water than air. It was shown the the speed of light in water was infact slower than in air.
TP Chapter 2 Q) What did Maxwell predict?
A) Light was made of transverse electromagnetic waves. He predicted the speed of all the waves and predicted there would be a spectrum of electromagnetic waves.
TP Chapter 2 Q) What two components make up EM waves and what is the phase difference between them?
A) Electric and magnetic waves have a phase difference of zero.
TP Chapter 2 Q) How was Maxwell's waves different than Huygens?
A) They were transverse instead of longitudinal.
TP Chapter 2 Q) How did Maxwell predict the speed of light?
A) c = 1/√μ0ε0
TP Chapter 2 Q) Who tested Maxwell's predictions?
TP Chapter 2 Q) How did Hertz detect radio waves?
A) Using a metal loop.
TP Chapter 2 Q) How did Hertz measure the speed of light using stationary waves?
A) Use c = f x λ, where wavelength is the distance between two antinodes.
TP Chapter 2 Q) How did Hertz show the transverse nature of the electromagnetic waves?
A) By showing the waves can be polarised.
TP Chapter 2 Q) How did Hertz show the magnetic nature of radio waves
A) Changing magnetic flux casued by the radiowave (created by a dipole) induced an EMF in a metal loop.
TP Chapter 2 Q) How did Hertz show the electric nature of radio waves
A) A second dipole aligned with the first would detect a changing electric field.
TP Chapter 2 Q) Why does the EMF drop to zero when the loop is rotated 90 degrees
A) Due to the dipole, the EM wave is polarised. If the loop is rotated 90 degrees there is now no change in magnetic flux to cause an EMF.
TP Chapter 2 Q) What is a blackbody?
A) An object that absorbs and emits all wavelengths
TP Chapter 2 Q) What is the ultraviolet catastrophe?
A) That with the classical interpration of light, it's intensity should tend to infinity near the ultraviolet wavelengths. This would violate the principle of energy conservation.