Light And Shadow Flashcards
What is a source of light ?
Sources of light are the things which can give out light. Sun is the ultimate source of light. Stars, glow worms and fireflies are natural sources of light while candle, tube light, bulb and torch are man made sources of light.
What are the sources of light ?
The sources of light are Candle power- measuring in comparison with candle. 1 candle power is 1256 lumen. Foot candles are lumen per unit area. 1 foot candle is 10.76 lux.
What are the types of light sources ?
The two types of light sources are incandescent source which releases both heat and light and cold sources which only releases light.
What are luminous and non luminous objects ?
Luminous objects are objects which can produce light. Example bulb, sun. No luminous objects don’t produce lights. Reflectors of light come under this category. Example book, moon.
What are the types of optical media ?
There are three types of optical media. They are - transparent which allows light to pass through , translucent which partially allows light to pass through and opaque which doesn’t allow light to pass through.
What is the rectilinear property of light?
Light only travels in a straight line. This is called the rectilinear property of light.
Explain the parts of shadows.
The parts of a shadow are its umbra and penumbra. Umbra is the dark shadow in the centre. Penumbra is the partial shadow formed around umbra. Near umbra, it is dark and it slowly merges and becomes brighter.
What is a shadow ? Write its properties.
The shadow of an object is formed in the direction opposite to the side of the light. When the source of light or object moves, the shadow shifts accordingly. The length of the shadow formed by sunlight changes with time.
Explain the positioning of the sun, moon and earth in the eclipses.
In lunar eclipse, the Earth is in between sun and moon. So, the earth’s shadow falls on the moon. In solar eclipse, the moon is in between the sun and earth. So, the moon casts its shadow on the earth.
Explain the colours of light.
When white light passes through a glass prism, it gets separated into 7 colors- violet, indigo, blue, green, yellow,orange and red. This is called the spectrum.
Explain pinhole camera briefly.
A pinhole camera consists of a closed box with a screen at one end and a small pinhole in the other end. The light which goes through the pinhole travels in straight lines and forms an image on the screen.
