A planet of mass M has a satellite of mass m, revolving around the planet in a circular orbit of radius r and time period T. The mass (M) of the planet is [AMU 2000]

(a) (b)

The age of universe is believed to be [NTSE 1995]

(a) 1 billion years (b) 10 billion years

A planet which is born sister of earth is [AFMC 2000]

(a) Mercury (b) Venus

Source of Sun’s energy is [CBSE PMT 1992;

KCET 1994; AFMC 1998; BHU 2000; DCE 2001]

(a) Burning of hydrogen

(b) Fission reactions involving hydrogen

(d) Some other source

Asteroids are [DPMT 2000]

(a) Small planets

(b) Shooting stars

(d) None of these

Sun radiates continuously and maintains its brightness because [MP PMT 1990; JIPMER 1997]

(a) Helium is converted into iron in its core

(b) Of fusion of hydrogen nuclei into helium

(d) Burning of carbon, in its core

Venus appears brighter than other stars because

[MP PMT 1990]

(a) It is heavier than other planets

(b) Its density is more than other planets

(d) Nuclear fusion takes place at its surface

There is no atmosphere on moon because [MP PMT 1990]

(a) There is no vegetation

(b) The escape velocity at its surface is very low

(d) There is vacuum in space

Which of the following planets have rings around it

[MP PMT 1991]

(a) Uranus (b) Mars

Milky way is [MP PMT 1991; Kerala PMT 2001]

(a) A planet of our system

(b) A sun

(d) One of the enormous galaxies of universe

Hubble’s law states that the velocity with which the ‘milky way’ is moving away from the earth is proportional to

[MP PMT 1991; Kerala PMT 2004]

(a) Square of the distance of the milky way from the earth

(b) Distance of milky way from the earth

(d) Product of the mass of the milky way and its distance from the earth

The hottest planet of solar system is [CBSE PMT 1992]

(a) Mars (b) Mercury

Towards the centre of sun [MP PMT 1992]

(a) Density decreases

(b) Pressure decreases

(d) Density and pressure increases

Period of revolution increases in the order of

[MP PMT 1992]

(a) Saturn, Uranus, Venus (b) Mars, Saturn, Pluto

The length of Milky way is [MP PMT 1992]

(a) 100,000 light years (b) 10,000 light years

Which of the nine planets is nearest to sun

[CBSE PMT 1992]

(a) Venus (b) Mercury

An extremely hot star would appear to be [AMU 1996, 97]

(a) Red (b) Blue

The sun emits a light with maximum wavelength 510 mm while another star X emits a light with maximum wavelength of 350 nm. What is the ratio of surface temperature of sun and the star X [AIIMS 2000]

(a) 2.1 (b) 0.68

A double star is a system of two stars rotating about their centre of mass only under their mutual gravitational attraction. Let the star have mass m and 2m and their separation be l. Their time period of rotation about their centre of mass will be proportional to [JIPMER 2000]

(a) (b) l

Hubble’s law is related with [AIIMS 2002; Pb. PET 2002]

(a) Comet (b) Speed of galaxy

‘Albedo’ is [Pb. PET 2001; BHU 2001;

Kerala PET 2002; AFMC 2002]

(a) Reflecting power of a heavenly body

(b) Transmitive power of a heavenly body

(d) Refracting power of a heavenly body

According to the pulsating theory the expansion and contraction of the universe repeats after every

[TNPCEE 2002]

(a) 11 years (b) 8 billion years

Meteors are [TNPCEE 2002]

(a) Small stars

(b) Burnt pieces of comets that fall on earth

(d) None of these

Which of the following helps us in the determination of the temperature of sun [CBSE PMT 2001]

(a) Kirchhoff’s law (b) Maxwell Boltzmann law

How does the red shift confirms that the universe is expanding [Pb. PMT 1997; AIIMS 2001]

(a) Due to Wien’s law (b) Due to Stefan’s law

Two stars P and Q are observed at night. Star P appears reddish while, star Q is white. From this we conclude

[Roorkee 1992]

(a) Temperature of Q is higher than that of P

(b) Temperature of Q is lower than that of P

(d) Star P is farther than star Q

Albedo is maximum for [Pb. PET 2000]

(a) Pluto (b) Venus

When original mass of star is greater than 5 M (M = mass of the sun). The death of this star will give rise to

[Pb. PET 2000]

(a) White dwarf (b) Black hole

The tail of the comet is due to [Pb. PET 2002]

(a) Vaporisation of water on the comet

(b) Sublimation of vapour in the comet

(d) Vaporisation of heat in the comet

In our solar system, there is one sun and [BHU 2004]

(a) Seven planets

(b) Nine planets

(d) Indefinite number of planets

Which one of the following planet has the longest day

[AFMC 2003]

(a) Venus (b) Mars

Which one of the following is known as Saptarishi

[AFMC 2003]

(a) Orion (b) Ursa major

Smaller pieces of heavy stones and metals which on entering earth’s atmosphere burns out are [AFMC 2003]

(a) Comets (b) Meteorites

In determining the temperature of a distant star, one makes use of [DCE 2003]

(a) Kirchhoff’s law (b) Stefan’s law

The motion of planets in the solar system is an example of conservation of [DCE 2001, 03]

(a) Mass (b) Momentum

Mass of earth has been determined through

[Kerala (Engg.) 2002]

(a) Use of Kepler’s T²/R constancy law

(b) Sampling the density of earth’s crust and using R

(d) Use of periods of satellites at different heights above earth’s surface

The galaxies are moving away from each other. It is explained by [DCE 2001]

(a) White dwarf star (b) Red shift

Speed of recession of galaxy is proportional to it’s distance

[DCE 1999]

(a) Directly (b) Inversely

Great bear is a [DCE 1998]

(a) Star (b) Galaxy

Surface temperature of the sun is of the order of [DCE 1996]

(a) 5000 K (b) 7000 K

The colour of a star is an indication of its[BCECE 2005]

(a) Weight (b) Distance

Which of the following is coldest planet[BCECE 2005]

(a) Mercury (b) Pluto

According to Hubble’s law, the redshift of a receding galaxy and its distance r from earth are related as

[AIIMS 2005]

(a) (b)

The condition for a uniform spherical mass m of radius r to be a black hole is [G = gravitational constant and g = acceleration due to gravity] [AIIMS 2005]

(a) (b)

Fraunhofer lines of the solar system is an example of

[AIIMS 2001]

(a) Emission spectrum

(b) Emission band spectrum

(d) Line absorption spectrum

The difference in the lengths of a mean solar day and a sidereal day is about [AIIMS 2003]

(a) 1 min (b) 4 min

A bright star is indicated to have a brightness magnitude of – 5 compared to a star of brightness zero magnitude. It means that this star compared to the reference star of zero brightness is [Kerala PMT 2003]

(a) 100 times less bright (b) 5 times more bright

The sun revolves around the galaxy with a speed of 250 km/sec and it’s radius is 3 ´ 10⁴ light year. The mass of the milky way is [BHU 1993]

(a) 3 ´ 10⁴⁰ kg (b) 3 ´ 10⁴¹ kg

There are certain types of stars called visible stars which undergo periodic change in their light output. If such a star quadruple it’s light output, how much does it’s magnitude change

(a) – 1.25 (b) – 1.5

A particular emission line, detected in the light from a galaxy, has a wavelength , where is the proper wavelength of the line. The galaxy distance from us

(a) (b)

Assuming that the dimmest visible star to the naked eye has a magnitude of about 6. Brightness of planet Venus (magnitude = – 4) w.r.t. this star is

(a) 10,000 times brighter (b) 2000 times brighter

A galaxy is observed to be moving with a velocity of 8600 km–sec^–¹. If it is at a distance of 430 million light year from us, Hubble constant and corresponding age of the universe are respectively

(a)

(b)

(c)

(d) None of these

Consider a binary star system consisting of two stars of masses and separated by a distance of 30 AU with a period of revolution equal to 30 years. If one of the two stars is 5 times farther from the centre of mass than the other. The masses of the two stars in terms of solar masses are

(a) 5, 15 (b) 25, 5

A planet of mass m moves in an ellipse around the sun of mass so that its maximum and minimum distances are and respectively. The angular momentum of the planet relative to the centre of the sun is

(a) (b)

The percentage of Sun’s total energy which reaches the earth’s surface is

(a) 10^–⁷ % (b) 10^–⁶ %

Suppose a planet goes around Sun with a linear speed twice as fast that of earth. What will be it’s orbit size as compared to that of earth ? (Radius of earth = R)

(a) R / 4 (b) R / 2

Read the assertion and reason carefully to mark the correct option out of the options given below:

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(d) If the assertion and reason both are false.

(e) If assertion is false but reason is true.

Assertion : The stars twinkle while the planets do not.

Reason : The stars are much bigger in size than the planets. [AIIMS 2003]

Assertion : A pulsor is a source of radio waves which change in terms of intensity at regular interval of time

Reason : A pulsor is a rotating neutron star

[AIIMS 1998, 2002]

Assertion : The comet do not obey Kepler’s laws of planetary motion

Reason : The comet do not have elliptical orbit

[AIIMS 1995]

Assertion : A star which appears blue will be much hotter than the sun

Reason : It is based on Wien’s law

Assertion : There is no atmosphere on moon

Reason : Escape velocity at the surface of moon is low.

Assertion : Red shift confirms that the universe is expanding

Reason : Wavelength of red light is maximum in the visible region

Assertion : Sun is at the galactic centre C of the milky way

Reason : All planets of solar system revolve around the sun.

Assertion : Moon is seen as it partly reflects the sun light falling on it

Reason : Moon is a satellite of earth. It does not emit light of its own

Assertion : The value of Hubble’s constant is 16 km/s

Reason : Hubble’s constant means that a galaxy at 1 million light years away is receding at the rate of 16 km/s.

Universe

1	d	2	d	3	b	4	a	5	b
6	d	7	a	8	b	9	d	10	b
11	c	12	a	13	c	14	b	15	c
16	a	17	b	18	c	19	b	20	d
21	d	22	b	23	b	24	d	25	b
26	a	27	b	28	b	29	b	30	d
31	b	32	a	33	d	34	b	35	d
36	d	37	a	38	b	39	b	40	a
41	b	42	a	43	b	44	b	45	c
46	c	47	c	48	b	49	a	50	c
51	c	52	c	53	b	54	a	55	c
56	d	57	b

Critical Thinking Questions

1	d	2	b	3	b	4	a	5	a
6	a	7	b	8	b	9	a	10	a

Assertion and Reason

1	b	2	b	3	b	4	a	5	a
6	b	7	e	8	a	9	e

Universe

(d) A study of binary star is most helpful in verifying Newton’s law of gravitation.
(d) A group of bright and faint stars is called a constellation
(b) The sky is divided into 88 constellations.
(a) Big Bang theory is the most satisfactory theory about the origin of universe.
(b) Venus is the brightest planet.
(d) A star which appears blue will be much hotter than the sun.
(a) When distant stars are receding from us, spectral line from the star, when compared to with the corresponding line from source will show red shift i.e. a shift in frequency towards the red end.
(b) Solar constant is the energy crossing per unit area per sec at earth’s distance, area being normal to the sun’s rays. Also energy falling is inversely proportional to the square of distance from the source.

(d) Venus and Mars have both CO₂ present.
(b) Þ Þ T = 10⁷ K
(c) Black hole is highly dense malter in the atmosphere which has very large value of gravitational pull, so that nothing escapes from it.
(a)
(c) The age of universe is believed to be 10-20 billion years.
(b) Planet Venus is called Earth’s sister.
(c) Source of Sun’s energy is fusion reactions involving hydrogen.
(a) Asteroids are a group of rock pieces moving around the Sun in between Mars and Jupiter. They are believed to be the remains of a large planet which exploded due to gravitative attraction of Sun and that planet, may be called small planets.
(b) The energy of the sun is due to fusion of hydrogen nuclei into helium.
(c) Venus appears brighter as it is nearest to the earth and the light of sun reflected form sun reaches earth with greater intensity.
(b)
(d) Saturn only has ring around it.
(d) Milky way is one of the enormous galaxies of the universe.
(b) According to Hubble’s law, v µ r.
(b) The hottest planet of solar system is one which is nearest to sun and has no atmosphere.
(d) As we move towards the centre of the sun, the density and pressure increases.
(b) As and distance of planet from sun in increasing order is for Mars, Saturn and Pluto.
(a) Length of milky way is 10⁵ light years.
(b) Mercury is the nearest planet to sun.
(b) According to Wien’s law, It means higher the temperature of a star, the lower is the wavelength of maximum intensity radiation emitted from star which tells the colour of star.
(b) As so
(d) or i.e.
(b) Speed of galaxy is proportional to it’s distance from us i.e. This is Hubble’s law
(a) Reflecting power of a heavenly body is called albedo.
(d)
(b) Meteors are burnt piece of comet. When they reach earth’s atmosphere, they start burning due to friction.
(d) According to Stefan’s law
(d) If the light received from galaxies indicates a shift towards the red end of spectrum of light, it means that the galaxies should be receding away (Doppler’s effect). Therefore we conclude that the universe is expanding.
(a) The star which appears red is at less temperature, than the star which appears white. Therefore, temperature of Q is higher than that of P.
(b) The albedo (reflection power) is maximum for Venus, because it reflects 85% of incident light. It’s value of albedo is 0.85.
(b) It is well known that if the mass of the star is more than that of mass of Sun, it explodes after it’s red giant stage and dies out giving rise to supernova and a black hole.
(a) If a comet approaches the sun, the substances like water etc. on the comet, get vaporised due to the heat of Sun, and radiation pressure forces of these vapours move away from the Sun. Hence, it forms the tail of the comet.
(b)
(a) Venus has the longest day.
(b) Ursa major is known as saptarishi.
(b)
(c) The temperature of stars can be determined by Wiens displacement law which is
(c) The motion of planets in the solar system is based on the conservation of angular momentum.
(c)
(b)
(a) Hubble’s law state that. Speed of recession (v) µ distance (r).
(c) Great bear is a constellation, which is a group of some stars.
(c) Surface temperature of Sun is about 6000 K.
(c) By using
(b) Because pluto is farthest from Sun.
(a) Hubble’s law is a statement of a direct correlation between the distance (r) to a galaxy and its recessional velocity as determined by the red shift (Z). It is stated as .
(c) The criterion for a star to be black hole is

or, .

(d) Fraunhofer lines are produced by the absorption of rays of the Sun in the atmosphere. When white light from photosphere passes through chromosphere, the vapours and gases present in it absorbs certain wavelengths and produces dark lines (Fraunhofer lines).
(b) The difference in the length of mean solar day and a sidereal day is about 4 min.

Critical Thinking Questions

(d) Given that magnitude for brightest star = – 5

and magnitude of given star = 0

Now m₂ – m₁ = 0 – (– 5) = 5

The brightness ratio is given by

So bright star is 100 time bright that the dim star.

(b) The mass of galaxy is given by

where v = 250 km/sec = 250 ´ 10³

r = 3 ´ 10⁴ ly = 3 ´ 10⁴ ´ 9.46 ´ 10¹² km » 3 ´ 10²⁰ m

\ » 3 ´ 10⁴¹ kg.

= .

(a) From Hubble’s law v = Hr where H = Hubble’s constant = 19.3 mm/sec–ly and r = Distance of Galaxy from us.

According to Doppler’s effect speed of Galaxy

(a) Here, for Venus , for star using .
(a)

Age of the universe,

Taking r = 430 ´ 10⁶ ly = 430 ´ 10⁶ ´ 9.46 ´ 10¹² km

If T is measured in years, r in A.U. and masses in Solar masses then .

…..(i)

Now

and

Again …..(ii)

After solving (i) and (ii) we get and

(b) From conservation of energy

. Angular momentum is conserved, that is

or Þ

(a) If S is the total energy emitted by Sun per second and r is the distance of earth from Sun; then energy reaching earth of radius R per second.

\Percentage of energy reaching earth

(a) From Kepler’s law and also

Þ Þ Þ

Assertion and Reason

(b) Stars twinkles due to variation in density of atmospheric layer. Also stars are much bigger in size than planets but it has nothing to deal with twinkling phenomenon.
(b) Pulsar is a source of radio waves which emits pulses of radio waves at short and regular time of intervals.

Pulsar is formed, due to super nova explosion, when super nova explosion occurs, the core of the star is compressed and electrons and protons combine to form a neutron. Due to this region pulsar is called neutron star.

(b) Comets do not revolve around the sun in fixed elliptical orbit like other planets and don’t obey Kepler’s law for planetary motion.
(a) According to Wien’s law, constant. As for the star is blue, which is less than for sun, which is yellow, therefore temp. T of star will be much higher than the temperature of the sun.
(a) At the surface of moon v_rms > v_escape hence molecules escape out before reaching their rms velocity that’s why there is no atmosphere present.
(b) Red shift means that wavelength of light received from stars is increasing i.e., apparent frequency is decreasing. Therefore, the stars/galaxies must be receding away. Hence the universe is expanding. Reason is also true, but it does not explain the assertion appropriately.
(e) The reason is true, but the assertion is false. Infect, distance of sun of our solar system from galactic centre is light years.
(a) Both the assertion and reason are true and reason is a correct explanation of the assertion.
(e) The assertion is not true. Infect, the value of Hubble’s constant is 16 km per sec per million light years.