Name any four man-made sources of light.
Four man-made sources of light include:
Incandescent light bulbs
Fluorescent lamps
LED lights
Streetlights
Give an example of an insect that emits light.
Fireflies are an example of insects that emit light.
If sunlight takes 8 minutes to reach the earth (and the speed of light is 3 lakh kilometers per second), calculate the distance of the sun from the earth.
Distance = Speed × Time
Distance = (3,00,000 km/s) × (8 × 60 seconds)
Distance ≈ 1,44,00,000 kilometers
State the difference between umbra and penumbra.
The umbra is the central, darkest part of a shadow where all light is blocked, while the penumbra is the outer part of the shadow where only a portion of light is blocked, resulting in a partial shadow.
Why do total and partial lunar eclipses occur?
Total and partial lunar eclipses occur when the Earth comes between the Sun and the Moon. In a total lunar eclipse, the Moon passes through the Earth’s umbra, while in a partial lunar eclipse, only a part of the Moon passes through the Earth’s umbra.
Why does a lunar eclipse not occur on every full-moon day?
A lunar eclipse does not occur on every full-moon day because the plane of the Moon’s orbit around the Earth is slightly tilted, so the Earth, Moon, and Sun are not always in perfect alignment. Only when they align in a straight line, and the Earth comes between the Sun and the Moon, does a lunar eclipse occur.
State the precautions to be taken for viewing partial or total solar eclipses.
It is dangerous to view a solar eclipse with naked eyes. Precautions include:
Using appropriate devices like solar viewing glasses.
Observing the eclipse indirectly by projecting an image of the Sun onto a screen using a pinhole camera or other devices.
Which type of surface is necessary for the phenomenon of reflection?
A shiny or polished surface is necessary for the phenomenon of reflection. Mirrors, water surfaces, and other reflective surfaces can change the direction of light through reflection.
