Do u think space research developing? (must readable one)  

Do u think space research developing?...I say yes bcoz nowa days lots of research going on in the space. do u think abt this?


This is the question asked for the competition...I'm in the competition. I know some answers only...do u help me by solving this with rough work? Bcoz they need the rough work also...

1 The luminosity of the Sun is 3.9 x 1033 ergs/sec (energy output per unit time). If the
radius of the Sun is 6.96 x 1010 cm and one assumes the Sun can be approximated
as a blackbody, choose the nearest effective temperature of the Sun from values
given below:
A] 5600 0K B] 5282 0K C] 5796 0K D] 6211 0K ANS:C

2 What is the minimum rotational period of a star whose density is 108 g/cm3?
A] 9.4 s B] 1.2 s C] 0.1 s D] 81.5 s

3 Crab nebula has a power law spectrum of the form dN/dE = 9.7 E- 2.1 photons/(cm2-
s-keV) where E is the energy of the photon. How many photons will a X-ray
detector operating in the energy range of 2-10 keV and geometric area of 30 cm2
detect in 100 seconds? (assume detector has 100% efficiency in this energy
range).
A] 10240 B] 1300 C] 30240 D] 650

4 What is the orbital period of a spacecraft orbiting the moon at an altitude of 200
km so that a given 20 km x 20 km patch on the lunar surface seen through a
detector on the spacecraft is viewed for 10 sec per orbit
A] 118 minutes B] 224 minutes
C] 91 minutes D] 66 minutes

5 A 100 cc volume of gas leaks from a container at the rate of 8.81 x 10-5 std cc/s.
The initial pressure of the gas is 800 torr. What would be the pressure after 30
days?
A] 78 Torr B] 782.6 Torr C] 812.3 Torr D] 550.4 Torr

6 How many primary electrons are generated when a 6 keV x-ray photon is incident
on a Silicon crystal of thickness 0.5 mm . Assume the Silicon crystal is fully
depleted due to the application of a voltage of 200 V (select the nearest answer)
A] 200 B] 20 C] 16200 D] 1630

7 Find the thickness of an aluminium sheet that can transmit only 10 % of 100 keV
incident photons.
A] 1 cm B] 5 cm C] 8 cm D] 0.2 cm

8 If the radius of earth were to shrink by one percent, its mass remaining the same,
the acceleration due to gravity at the earth’s surface would
A] decrease B] remains
Unchanged
C] increase D] none ANS: C

9 An electric bulb of volume 250cm3 was sealed off during manufacture at the
pressure of 10-3 mm of Hg at 27°C. Number of air molecules in the bu lb are
A] 8.018 X 1015 B] 80.18 X 1015 C] 801.8 X 1015 D] 0.8018 X 1015

10 A proton moving with a constant velocity passes through a region of space
without any change in its velocity. If E and B represent the electric and magnetic
fields respectively, this region of space may have
A] E = 0, B = 0 B] E = 0, B ? 0 C] E ? 0, B = 0 D] E ? 0, B ? 0

11 When a ray of light enters a glass slab from air
A] its wavelength decreases B] its wavelength increases
C] its frequency increases D] neither wavelength nor frequency
changes ANS:D

12 An astronomical telescope has an angular magnification of magnitude 5 for
distant objects. The separation between the object and the eyepiece is 36cm and
the final image is formed at infinity. The focal length f0 of the object and the
length fe of the eyepiece are:
A] f0 = 45 cm and fe = -9 cm B] f0 = 50 cm and fe = 10 cm
C] f0 = 7.2 cm and fe = 5 cm D] f0 = 30 cm and fe = 6 cm

13 The sample of a radioactive substance has 106nuclei. Its half life is 20 seconds.
The number of nuclei that will be left after 10 seconds is
A] 1 X 105 B] 2 X 105 C] 7 X 105 D] 11 X 105

14 If elements with principal quantum number n > 4 were not allowed in nature, the
number of possible elements would be
A] 60 B] 32 C] 4 D] 64

15 An a particle of energy 5 MV is scattered through 180° by a fixed uranium
nucleus. The distance of closest approach is of the order of
A] 1 Å B] 10-10 cm C] 10-12cm D] 10-15cm