### 2018-19 അധ്യയനവര്‍ഷത്തില്‍ എല്ലാ അധ്യാപകര്‍ക്കും വിദ്യാര്‍ഥികള്‍ക്കും physicscare- ന്റെ ആശംസകള്‍ . ### ### ### ###

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Do You Know


What does a fish see when it looks up from the pond?
The fish sees a circle of light directly above and can see the pond surroundings (the bank, the trees, etc.) in this circle. Beyond this circle the surface of the water acts as a mirror, due to total internal reflection, and other fish in the water will be reflected in it. The radius of the circle depends on the refractive index of the water and the depth of the fish below the surface.

Why are you advised not to water plants on a bright sunny day?
The water forms droplets on the leaves. These droplets act as converging lenses and focus the sun onto the leaves, burning them. As a result the leaves will have brown spots.

Why are soap bubbles coloured in white light?
The light waves reflected from the front and back surfaces of the bubble interfere, resulting in different colours being in phase at different angles.

What would a soap bubble look like in monochromatic sodium light?
A soap bubble would appear as yellow and black horizontal stripes due to constructive and destruc- tive interference.

How would a rainbow appear to passengers in an aeroplane when there is rain in the air above and below them?
It should appear as a complete circle as the rays reaching the passengers from all directions which are at an angle of 42° with the line from the sun to the aircraft will display the rainbow .

Why is the filament of an electric light bulb coiled?
The filament is coiled to reduce heat loss, the higher the temperature the whiter the light. If the filament is uncoiled then it will only glow dimly.

2 comments:

  1. why plants adjust the water intake when we give more water?

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    1. Plants take in water through their roots, and green ones use it in photosynthesis, which is how they create sugar for food. Plants also need water to support themselves. Pressure from the process of osmosis -- the movement of water from the outside to the inside of the plant's cells -- keeps up the plant's cell walls.
      When you water a plant, it sucks up the water through capillary action. Then the water travels from the roots through tubes called xylem vessels. Water reaches the leaves of the plant and escapes through small holes called stomata, which open when the plant needs to cool down. This process is called transpiration and is similar to how people (and some animals) sweat. Carbon dioxide also enters the plant through the stomata.
      Some plants have also found unique ways to live with little or no water. One way is a variation of photosynthesis called Crassulacean Acid Metabolism (CAM) photosynthesis. In CAM photosynthesis, a plant stores carbon dioxide as acid and keeps its stomata closed during the day to save water (evaporation happens at a slower rate at night). It can even keep its stomata closed at all times if conditions are especially arid. Cacti use CAM photosynthesis to survive the extreme heat and drought of the desert.

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