shadows d. crowley, 2008. shadows to know how shadows are formed
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D. Crowley, 2008
To know how shadows are formed
• What is light?
• How does it travel, and at what speed?
• How can we see objects?
• Do all objects give out light?
• Discuss what you know about light with your partner…
• Light carries energy and travels as a wave
• Light travels extremely quickly - 300,000 km/s (much faster than sound - think about fireworks / thunderstorms)
• Light waves travel in straight lines (it cannot bend around corners)
• Why do shadows form?
• Light travels in straight lines (it cannot bend around corners)
• Shadows form because light cannot bend round behind an object
• Some objects are known as luminous
• A luminous object gives out light (a light source), such as: -• Fires• Light bulbs• Stars (e.g. the Sun)
• How does light travel from a luminous object to our eye?
Light travels in a straight line, directly to your eye
• Most objects are non-luminous
• A non-luminous object does not give out light
• We see non-luminous objects by light from a luminous object hitting the non-luminous object and reflecting into our eye
• How does light travel from a non-luminous object to our eye?
Light from the luminous object hits the non-luminous object, reflecting light into our eye
• Opaque - materials which do not allow light to pass through them (e.g. a brick wall)
• Transparent - materials which do allow light to pass through them (e.g. a glass window)
• Translucent - materials which only allow part of the light to pass through them (e.g. paper)
• Complete the casting shadows worksheet
• Shadow of full milk bottle is much bigger, as no light is passing through (opaque)
• Drinking class is transparent, allowing light through (so shadow is just an outline, unlike the full shadow of the opaque mug)
• Empty cola bottle has only an outline shadow, unlike the full shadow of the full cola bottle
• If the lamp is raised the shadows become smaller
• If the lamp is lowered the shadows become bigger