VISUAL PHYSICS ONLINE

7.1 THE NATURE OF LIGHT

P71 017

Two unmarked and apparently identical lamps are supplied. Only one of the lamps emits polarised light. Two similar plastic sheets are supplied, only one of which is a piece of polaroid.

(A)

Describe how you could identify the lamp producing the polarised light and the polarised sheet.

(B)

Without using the lamps, how could you distinguish between the two plastic sheets.

View solution below only after you have completed answering the question. The solution is not in a form that you would answer in an examination. The answers are often in more detail to help improve your appreciation and understanding of the physics.

Solution

(A)

Observe each lamp through each plastic sheet. As the polaroid sheet is rotated in front of the polaroid lamp, the transmitted light will vary from dark to light to dark … .

(B)

Observe an alternative source of polarised light. For example, light scattered from the sky or light reflected form a non-metallic surface. The light transmitted through the polaroid sheet will vary from light to dark as the sheet is rotated.

Polarised light as viewed through a polaroid sheet as it is rotated.