Diagnostic questions on superposition

What the Activity is for

Diagnostic questions exploring the diffraction, interference and polarisation of waves.

The diagnostic questions can be used for two main purposes:

• To encourage students to talk about and think through their understandings of the diffraction, interference and polarisation of waves.
• To provide the teacher with formative assessment information about the students' understandings of the diffraction, interference and polarisation of waves.

What to Prepare

• printed copies of questions on diffraction, interference and polarisation (see below)

What Happens During this Activity

We'd suggest getting the students to work in pairs on these questions, encouraging them to talk through their ideas with each other. Collect responses from all of the pairs and discuss in a whole-class plenary.

Alternatively, the questions might be set for homework prior to the lesson, so that you have time to read through the responses.

Question 1: The spreading of a wave through a gap in a barrier is called:

1. interference.
2. superposition.
3. dispersion.
4. diffraction.

Answer 4.

Question 2: Light passing through a small pinhole does not make a shadow with a distinct, sharp edge because of:

1. refraction.
2. diffraction.
3. polarisation.
4. interference.

Answer 2.

Question 3: A train of water waves travels from an area of deep to shallow water, crossing the boundary at right angles. Which of the following statements is/are correct:

1. The water waves change direction as they meet the boundary.
2. The water waves do not change direction as they meet the boundary.
3. The water waves speed up as they meet the boundary.
4. The water waves slow down as they meet the boundary.

1. 1 only.
2. 2 only.
3. 1 and 3.
4. 2 and 4.

Answer 4.

Question 4: Which of the following kinds of waves can show interference effects?

1. sound
2. water
3. infrared

1. 1 only.
2. 1 and 3 only.
3. 2 only.
4. 1, 2 and 3.

Answer 4.

Question 5: Which of the following settings in a ripple tank will produce the most prominent diffraction pattern of a water wave of wavelength of 2 cm?

1. The wave passes through a gap of 20 cm.
2. The wave passes through a gap of 10 cm.
3. The wave passes through a gap of 4 cm.
4. The wave passes through a gap of 2 cm.

Answer 4. For maximum spreading to occur the size of gap needs to be the same as or smaller than the wavelength.

Question 6: The polarisation of light is best explained by thinking about light as being:

1. a longitudinal wave.
2. a transverse wave.
3. a transverse wave with components in different planes.
4. a stream of energy photons.

Answer 3.

Question 7: Light is passed through a polarising filter with its transmission axis in the horizontal plane. It then passes through a second filter with its transmission axis in the vertical plane. After passing through both filters the light will be:

1. polarised.
2. unpolarised.
3. entirely blocked.
4. returned to its original state.

Answer 3.