Advertisements
Advertisements
प्रश्न
Consider a sunlike star at a distance of 2 parsecs. When it is seen through a telescope with 100 magnification, what should be the angular size of the star? Sun appears to be (1/2)° from the earth. Due to atmospheric fluctuations, eye can’t resolve objects smaller than 1 arc minute.
Advertisements
उत्तर
The angle of the sun's diameter `(1/2)^circ` is subtended by 1 A.U. since the distance from the sun increases angle subtended in the same ratio.
Now, 2 x 105 A.U. will from an angle of θ = `(1/(4 xx 10^5))^circ`, since the diameter is the same angle subtended on earth by 1 parsec will be same.
If the sunlike star is at 2 parsec the angle becomes half = (1.25 × 10–6)°
Thus, angle = 75 × 10–6 min
When it is seen with a telescope that has a magnification of 100, the angle formed will be 7.5 × 10–3 min, viz., less than a minute.
Hence, it can't be observed by a telescope.
APPEARS IN
संबंधित प्रश्न
While measuring the length of an object using a ruler, the position of your eye should be
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?
Match the following.
| 1. | Length | kelvin |
| 2. | Mass | metre |
| 3. | Time | kilogram |
| 4. | Temperature | second |
Now guess the length and width of many other things. Measure and find the difference between your measure and your guess.
| Size of | Your guess in cm | Your measure in cm | ||
| Length | Width | Length | Width | |
| 100 Rupee note | ||||
| 10 Rupee note | ||||
| 20 Rupee note | ||||
| 5 Rupee note | ||||
| Post card | ||||
| Math-Magic book | ||||
Measure the yellow rectangle. It is ________ cm long.
How close was your earlier guess? Discuss.
Can you think of how to cut a postcard so that you can pass through it?
There are two beautiful lakes near a village. People come for boating and picnics in both the lakes. The village Panchayat is worried that with the noise of the boats the birds will stop coming. The Panchayat wants motorboats in only one lake. The other lake will be saved for the birds to make their nests.
- A longer boundary around the lake will help more birds to lay their eggs. So which lake should be kept for birds? Which lake should be used for boats?
In which SI unit, you can measure your height?
What are the materials needed to find the length of a banana?
What formula is used to measure the area of your classroom?
What is the unit of measurements of very small lengths?
The distance between one end and the other end is called ______.
The SI unit of mass is kg.
- The earth-moon distance is about 60 earth radius. What will be the diameter of the earth (approximately in degrees) as seen from the moon?
- Moon is seen to be of (½)°diameter from the earth. What must be the relative size compared to the earth?
- From parallax measurement, the sun is found to be at a distance of about 400 times the earth-moon distance. Estimate the ratio of sun-earth diameters.
Mars has approximately half of the earth’s diameter. When it is closest to the earth it is at about 1/2 A.U. from the earth. Calculate what size it will appear when seen through the same telescope.
If a planet subtends an angle α at distance D, what formula is used to find the planet's diameter?
What is an Astronomical Unit (AU)?
Which instruments are used to measure very small distances at the atomic scale?
