Which of these devices in your everyday life make use of polarization of light?

Question

Which of these devices in your everyday life make use of polarization of light? a. Transitions brand glasses that darken in sunlight and lighten indoors. b. Laser pointers and lasers in grocery store scanners. c. Holographic images on credit cards. d. Liquid crystal laptop displays. e. Holiday icicle lights. Thinking of the cases from the Lens Chart last week, a compound microscope from a biology lab makes use of a nosepiece objective lens acting in case __, and an eye lens in case __. a. 2, 5 b. 5, 7 c. 2, 7 d. 2, 1 e. 5, 1 An inexpensive telescope has an objective lens with a diameter of 50 mm and a focal length of 500 mm, coupled with an eye lens of diameter 12 mm and focal length of 25 mm. It would magnify an image by a factor of a. 2. b. about 4. c. 20. d. about 42. We always assume that light travels in perfectly straight lines, so much so that we use lasers as levels for accurate construction. Why do we think that light always travels in straight lines? a. Its wavelength is so very small. b. The gravitational field of the earth is weak. c. It only refracts when changing media. d. Because of all of these!

Explanation / Answer

1) (d)Liquid crystal laptop display.

LCDs make use of plarizers.

2) Need lens chart for this.

3)(c) 20

Given, focal length of the objective Fo = 500mm

focal length of the eyepiece Fe = 25mm

We have for telescope: Magnification M = Fo/Fe = 500/25 = 20

4) (b) The gravitational field of the Earth is weak.

1. Let's say for example an electric current is passed through a wire, a magnetic field is produced around it. (This is given by the Right hand screw rule)

2. To compensate this, an electric field is generated in the direction of blocking a change in the magnetic field.

3. To compensate this, a magnetic field is generated in the direction of blocking a change in the electric field.

And this cycle goes on, leading to the formation of electric and magnetic fields repeatedly causing a propagation of the wave.

The source of the first field could be something else too (not just current through a wire). However, the successive fields produced (as per its existence) are always perpendicular to each other. As a result, it will propagate straight.

This is possible only if the Earth’s gravitational field is weak.

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