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15 Cards in this Set
- Front
- Back
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What is a ray diagram? |
A ray diagram shows how light travels, including what happens when it reaches a surface. In a ray diagram, you draw each ray as a straight line with an arrowhead pointing in the direction that the light travels. |
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Draw a ray diagram to show: The incident ray, the reflected ray, the normal and the angles of incidence and reflection as light reflects off the surface of a mirror. |
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Explain the components of your ray diagram. |
In the ray diagram:the hatched vertical line on the right represents the mirror. The dashed line is called the normal, drawn at 90° to the surface of the mirror. The angle of incidence, i, is the angle between the normal and incident ray. The angle of reflection, r, is the angle between the normal and reflected ray. The law of reflection states that the angle of incidence equals the angle of reflection, i = r. For example:the angle of reflection is 30° if the angle of incidence is 30° |
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What is scattering? |
If light meets a rough surface, each ray obeys the law of reflection. However, the different parts of the rough surface point in different directions, so the light is not all reflected in one direction. Instead, the light is reflected in all directions. |
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Use a ray diagram to explain what you see when an object is reflected in a plane mirror. |
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Describe how the image looks. |
The image: Appears to be behind the mirror. Is the right way up. Is ‘laterally inverted’ (left and right swapped over) |
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Explain the difference between 'real' and 'virtual' rays. |
‘Real’ rays, the ones leaving the object and the mirror, are shown as solid lines.
The ‘virtual’ rays, the ones that appear to come from the image behind the mirror, are shown as dashed lines. |
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In a camera, is the image produced 'real' or 'virtual'? |
It is a real image because the rays of light do pass through it. |
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Which way up is the image in: (a) A plane mirror? (b) A camera? |
(a) Upright (b) Upside down (inverted). |
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A mug is 8 cm tall, and you place it 10 cm from a mirror. (a) How tall does the mug appear to be in the mirror? (b) How far from the mirror does the image of the mug appear to be? (c) Isthe image real or virtual? |
(a) 8 cm (b) 10 cm (c) Virtual. |
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Complete the Figure to show how the periscope can be used to see over a high wall. |
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An optician’s chart is on the wall 1 m behind the patient’s head. The patient sees the chart in the mirror, which is 2.5 m away in front of the patient. How far away does the image of the chart appear to be from: (a) the chart? (b) the patient? |
(a) 7 m (b) 6 m |
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The photograph shows a meter with a mirror behind the pointer. Explain how the mirror helps to read the meter accurately. |
When you line up the pointer exactly over its reflection then your eye is directly above the pointer and you will be reading the scale accurately (this is called no parallax). |
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Describe how a digital camera produces an image of the object being photographed. |
Rays of light from the object enter the camera through the lens, and form an image. The image is real and is inverted. Using a lens gives a sharp and bright image. The image is recorded by light-sensitive electronic sensors. The information is stored in some form of memory device. |
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What are the key points to remember? |
The angle of incidence i = the angle of reflection r. The image in a plane mirror is upright and virtual. Visible light is used in photography. The image formed by a camera is real and inverted. |
