- State the law of
reflection. (lesson 29a)
- An object is placed 20cm
in front of a plane mirror. Where does the image appear to be? (29a)
- A light ray enters a
glass block and is refracted. Is it bent towards or away from the normal
line? (29a)
- Name 2 types of lens, and
say what they do. (29a)
- Explain how how you can
see the writing on a piece of paper. (29b)
- A camera and the eye both
use a lens to focus an image. How are they a) similar, b) different? (29b)
- Name the colours of the
spectrum. (29c)
- What colours are absorbed
by a red filter? (29c)
- Why does a red shirt
appear red? (29c)
- What colour would a red
shirt appear in blue light? (29c)
- Explain how you can hear
a dog barking - starting with how the sound is produced by the dog. (29d)
- Why can't sound sound
travel through a vacuum? (29d)
- How does hte loudness of
a sound depend on the amplitude of the wave? (29d)
- How doe the pitch of a
sound depend on the frequency of the vibration? (29d)
- Why do you see a
lightning flash before you hear the thunder? (29e)
ANSWERS
- The angle of reflection
is always equal to the angle of incidence.
- 20cm behind the mirror.
- When light enters glass
it is bent towards the normal line.
- Convex and concave.
Convex converges the rays, concave diverges the rays.
- Light rays are reflected
from the page into the eye. The rays are focussed to an image on the retina
and the signals are sent to the brain along the optic nerve.
- Both lenses are convex.
In the eye the lens changes shape, in a camera the lens to a different
position to focus the image.
- Red, orange, yellow,
green, blue, indigo, violet. (ROY G BIV)
- Orange, yellow, green,
blue, indigo and violet are absorbed. Only red passes through.
- It reflects red light and
absorbs all other colours.
- Black.
- The dogs vocal cords are
vibrating, sending a wave through the air. The air molecules vibrate. The
energy is transferred from molecule to molecule. Some of the energy is
transferred to the ear-drum causing it to vibrate., the signal is then
passed to the brain.
- There are no molecules to
vibrate, so no energy is transferred.
- The bigger the amplitude
the louder the sound.
- The higher the frequency,
the higher the pitch.
- Light travels faster than
sound.
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