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प्रश्न
While measuring the length of an object using a ruler, the position of your eye should be
पर्याय
left side of the point.
vertically above the point where the measurement is to be taken.
right side of the point.
any where according to one’s convenience.
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उत्तर
vertically above the point where the measurement is to be taken.
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संबंधित प्रश्न
The principle of ‘parallax’ in section 2.3.1 is used in the determination of distances of very distant stars. The baseline AB is the line joining the Earth’s two locations six months apart in its orbit around the Sun. That is, the baseline is about the diameter of the Earth’s orbit ≈ 3 × 1011m. However, even the nearest stars are so distant that with such a long baseline, they show parallax only of the order of 1” (second) of arc or so. A parsec is a convenient unit of length on the astronomical scale. It is the distance of an object that will show a parallax of 1” (second) of arc from opposite ends of a baseline equal to the distance from the Earth to the Sun. How much is a parsec in terms of meters?
Match the following.
| Column A | Column B |
| (1) Length | a. kilogram |
| (2) Mass | b. cubic metre |
| (3) Area | c. metre |
| (4) Volume | d. square metre |
Solve the numerical example.
When the planet Jupiter is at a distance of 824.7 million kilometers from the Earth, its angular diameter is measured to be 35.72'' of arc. Calculate the diameter of Jupiter.
A hand span is a reliable measure of length.
While measuring the length of a sharpened pencil, the reading of the scale at one end is 2.0 cm and at the other end is 12.1 cm. What is the length of the pencil?
How many stamps are needed to cover the rectangle?
How close was your earlier guess? Discuss.
According to the modern definition, what fraction of a second does light travel to define one metre?
If a planet subtends an angle α at distance D, what formula is used to find the planet's diameter?
Why is the speed of light used to define the metre?
