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 5005?
Round up the following upto three significant figures:
10.4107
Round up the following upto three significant figures:
0.04597
Round up the following upto three significant figures:
2808
How many significant figures should be present in the answer of the following calculation:-
`(0.02856 xx 298.15 xx 0.112)/0.5785`
The photograph of a house occupies an area of 1.75 cm2on a 35 mm slide. The slide is projected on to a screen, and the area of the house on the screen is 1.55 m2. What is the linear magnification of the projector-screen arrangement?
Precise measurements of physical quantities are a need of science. For example, to ascertain the speed of an aircraft, one must have an accurate method to find its positions at closely separated instants of time. This was the actual motivation behind the discovery of radar in World War II. Think of different examples in modern science where precise measurements of length, time, mass etc. are needed. Also, wherever you can, give a quantitative idea of the precision needed.
State the number of significant figures in the following:
6.032 N m–2
State the number of significant figures in the following:
0.0006032 m2
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.
Which of the following has the highest number of significant figures?
The radius of the circle is 3.12 m. Calculate the area of the circle with regard to significant figures.
Write a short note on the following.
Rounding - off
Assertion (A): Significant figures for 0.200 is 3 where as for 200 it is 1.
Reason (R): Zero at the end or right of a number are significant provided they are not on the right side of the decimal point.
If the density of a solution is 3.12 g mL–1, the mass of 1.5 mL solution in significant figures is ______.
The sum of the numbers 436.32, 227.2 and 0.301 in appropriate significant figures is ______.
Which of the following measurements has exactly two significant figures?
The radius of Earth is written as 0.64 × 10⁷ m in scientific notation. What is its order of magnitude?
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?
