MQUD - WORKSHEET 4
MQUD – WORKSHEET 4 – Malus’ Experiment and the ideal situation
A_A beam of polarized light with intensity Iostrikes a Polaroid, whose co-efficient of transmission is T. Through the experiment it was found that the intensity of light transmitted is given by:
IT()=Io T cos2
A1_Which aspect of the phenomenologyis described by T (the physics significance of T)? ______
______
-Its experimental value is always: > 1 < 1 = 1
Explain your response: ______
______
A2_ Which aspect of the phenomenology is described by the factor ? ______
We shall review the experiments following the hypothesis that light is composed of photons, which are always revealed as single and discreet entities ( Photons are never revealed in units of 1 ½).
The light intensity is proportional to the number of photons.
B_IDEAL POLAROIDS
B1_ A beam of N photons, filtered by a first polaroid which vertically polarizes the light (polaroid V), strikes an ideal polaroid F2 (T=1) rotated 45° with respect to V. With a ?detector? placed beyond F2 we may measure the number of photons transmitted.
- What will be the number NTof photons that will be transmitted by F2? NT = ______
B2_What direction of polarization will the beam have when the ratio NT / N
is equal to: 1? ______; 0? ______1/2? ______
B3_ We will now consider the case where the beam is of low intensity, or rather,if only one photon at a time interacts with the polaroid (and eventually the ?detector?), for each of the N photons of the beam. In this case do we have to change our answers to questions B1 and B2? (Explain your reply)
______
______
B3_A beam of N polarized photons following the vertical direction V strikes an ideal Polaroid (T=1) with an preferred rotation with respect to V.
- What information does Malus’ law provide about the survival of each photon? ______
B4_What is the probability that a photon from a beam polarized at 45°will be transmitted through an ideal polaroid (T=1) with the preferred direction:
- vertical? ______horizontal? ______at 45°? ______
2.2 REAL POLAROIDS
A_ A beam of light polarized according to a definite direction (for example direction V) composed of N photons strikes a real polaroid (ex. T=0.7)
- What is the probability that a photon from the beam is transmitted through the polaroid?
With the preferred direction V? ______
With the preferred direction H (horizontal)? ______
With the preferred direction at 45° with respect to V? ______
B_In the case of real polaroids (ex. T=0.7) it is possible to have a probability of transmission:
- Equal to 1? Yes No
Explain: ______
- Equal to 0? YesNo
Explain: ______
C_ In the case of real polaroids (ex: T=0.7):
- What is the maximum value of the probability of transmission of a photon? ______
- When is this obtained? ______
D_What information about the survival of a single photon is provided by the ratio in this case?
______
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