Advertisements
Advertisements
प्रश्न
A LASER is a source of very intense, monochromatic, and unidirectional beam of light. These properties of a laser light can be exploited to measure long distances. The distance of the Moon from the Earth has been already determined very precisely using a laser as a source of light. A laser light beamed at the Moon takes 2.56 s to return after reflection at the Moon’s surface. How much is the radius of the lunar orbit around the Earth?
Advertisements
उत्तर १
Time taken by the laser beam to return to Earth after reflection from the Moon = 2.56 s
Speed of light = 3 × 108 m/s
Time taken by the laser beam to reach Moon = `1/2 xx 2.56 = 1.28 s`
Radius of the lunar orbit = Distance between the Earth and the Moon = 1.28 × 3 × 108 = 3.84 × 108 m = 3.84 × 105 km
उत्तर २
We known that speed of laser light = c = 3 x 108 m/s. If d be the distance of Moon from the earth, the time taken by laser signal to return after reflection at the Moon’s surface
t =2.56 s = `(2d)/c = (2d)/(3xx10^8 ms^(-1))`
`=> d = 1/2 xx 2.56 xx 3 xx 10^(8) m = 3.84 xx 10^8 m`
संबंधित प्रश्न
What do you mean by significant figures?
How many significant figures are present in the 208?
How many significant figures are present in the 5005?
How many significant figures are present in the 500.0?
You are given a thread and a metre scale. How will you estimate the diameter of the thread?
The mean diameter of a thin brass rod is to be measured by vernier callipers. Why is a set of 100 measurements of the diameter expected to yield a more reliable estimate than a set of 5 measurements only?
A man walking briskly in rain with speed v must slant his umbrella forward making an angle θ with the vertical. A student derives the following relation between θ and v: tan θ = v and checks that the relation has a correct limit: as v →0, θ → 0, as expected. (We are assuming there is no strong wind and that the rain falls vertically for a stationary man). Do you think this relation can be correct? If not, guess the correct relation.
It is a well known fact that during a total solar eclipse the disk of the moon almost completely covers the disk of the Sun. From this fact and from the information you can gather from examples 2.3 and 2.4, determine the approximate diameter of the moon.
State the number of significant figures in the following:
0.007 m2
State the number of significant figures in the following:
2.64 × 1024 kg
State the number of significant figures in the following:
6.032 N m–2
Solve the numerical example.
Nuclear radius R has a dependence on the mass number (A) as R =1.3 × 10-16 A1/3 m. For a nucleus of mass number A = 125, obtain the order of magnitude of R expressed in the meter.
Solve the numerical example.
Write down the number of significant figures in the following: 0.003 m2, 0.1250 gm cm-2, 6.4 x 106 m, 1.6 x 10-19 C, 9.1 x 10-31 kg.
The radius of the circle is 3.12 m. Calculate the area of the circle with regard to significant figures.
Calculate the length of the arc of a circle of radius 31.0 cm which subtends an angle of `pi/6` at the centre.
Significant figures in a measurement include which of the following?
Which of the following measurements contains exactly two significant figures?
The arithmetic mean of three measurements, 15.4 cm, 15.4 cm, and 15.5 cm, is 15.43 cm. How many significant figures does this result have?
The radius of Earth is expressed as 0.64 × 10⁷ m in scientific notation. What is its order of magnitude and number of significant figures?
