The Sun
I.
Fill up the blanks
1. Aurora effect can be demonstrated in the science laboratory also by ionizing certain
gases by high volume.
2. The colour of chromosphere is pink.
3. Solar flares are associated with intense magnetic field.
4. Sun is called the laboratory to study other stars because Sun is nearer to earth.
5. The reason for enormous energy output of the sun is formation of helium.
6. Harmful effect of solar wind on earth is protected by magnetosphere.
7. Sun spots on the photosphere are due to comparatively cooler regions.
II.
Fill up the blanks
1. The innermost layer of the sun is called the core.
2. The zone that provides an efficient means of transporting energy near the core of
the sun is radiation zone.
3. The solar wind consists of hydrogen nuclei or protons.
4. The visible surface of the sun is photosphere.
5. Corona of sun is visible during total solar eclipse.
III
Answer the following
1. Distinguish between solar flares and solar prominences.
A. Solar flares- Due to variation in the electromagnetic field on the photosphere sudden but
short sudden but short lived outbursts of energy and matter spurt from the surface of the
sun. This is called solar flare.
Solar prominences – Sometimes matter in the form of hydrogen clouds loop out and loop
back into the photosphere in spectacular shapes known as solar prominences.
2. What are sun spots? To which factor are they related?
A. Sunspots are dark irregular patches or spots on the photosphere. They are related to
i)Temperature ii)Magnetic field
3. State Kepler’s 3 laws of planetary motion.
A. 1st law  Each planet moves in an elliptical orbit, with the sun at one focus of the ellipse.
2nd law  The line joining the planet to the sun sweeps out equal areas in equal intervals
of time as planet travels around the ellipse.
3rd law  The square of the orbital period of a planet is proportional to the cube of the
semi major axis of the orbit.
Q IV Explain the structure of sun with a neat diagram.
For diagram refer page no.374
fig 27.7
The visible disc of the sun is photosphere which has grain like structures are called
Granulations and thread like structure called spicules. It has irregular dark patches called
sun spots. Inner most layer is the core surrounded by radiation zone and convection
zone. The solar atmosphere just above the photosphere is called chromospheres.
Q 5 State the effects of solar activities.
Some time the charged particles from the sun cause variations in the of earth’s
ionosphere and ionosphere is affected by these changes. Aurora is a colourful display in
the sky caused by ionization of gases near the polar regions of the earth caused by the
charged particles of the solar wind.
Q 6 Draw the neat diagram of total solar eclipse showing the corona of the sun.
For diagram page no. 369 Fig 27.1
Q 7 State the layer of earth’s atmosphere which protects us from the radiation of the
sun
i)Ozone layer found in stratosphere ii) Magnetosphere
Q 8Name the nuclear fuel present in the sun
The nuclear fuel present in the sun is hydrogen.