1. Explain the difference bebween a wave of light and a \'photon of light. What
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1. Explain the difference bebween a wave of light and a 'photon of light. What is particlee D uaity? 2. What is destructive and constuctive interference?What are the physical requirements for two waves to interfere destrucivety and constructiv ely? What is D iffraction and what are the conditons for it to occur (consider a single slit)? 3. Consider two slits; find an expression for destructive and corstuctve inference for a screen s everal meters away (you do not have to derive it, instead you can reference a source). 4. Find an expression for single slit diffr action using the quantum model of light 5. To understand the implications of light leaks, and to use some numbers typical of the PMT in this apparatus, suppos e th at full sunlight delivers 1000 /m 2to the earth, and that full moonlight is a million times dimmer. Suppose that this moonlight is delivered by photons of yellow light, that they fall on a photocathode of area 8×25 mm12, and that they are converted to photoelectrons with efficiency 4%. Suppose finally that each photoelectron emitted at the photocathode is amplifed to a pulse of 10A6 electrons arriving at the anode. C alculate: a) the arrival rate of photons at the photocathode, b) the emission rate of photoelectrons, c) the arrival rate of electrons atthe anode, and d) the average anode currentthis represents; finally, compare that current with the manufacturers suggested limit of 1A for average anode current. 6. In asingle measurement, 1000 photons were counted to hit a detector. What is the expected standard deviation in the count if the s ame measurement were repeated many times? (see Taylor section 3.2 for a hint)Explanation / Answer
1. Light can be defined as an electromagnetic wave. In this approach, a changing electric field creates a changing magnetic field. This changing magnetic field then creates a changing electric field, eventually leads to light. Light does not need a medium to propagate. The light has a particular wavelength and speed in any medium. It will behave as a wave and show the properties of interference and diffraction, which are exclusive to a wave.
While light is a wave, it also shows the property of a photon of light. When the light falls on the detector, the energy contained in the light wave are transferred like a packet or burst at a time. This phenomenon is called as the Photoelectric effect. In this case, the energy of each particle is equal to the product of Planck constant the frequency of the light. This is the minimum quanta of light that is absorbed or emitted.
The above two reasons forms the basis for wave-particle duality. When the wave propagates in free space, it describes the wave phenomena. However at the time of detection, it behaves as a particle.
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