Why is the distance between stars expressed in light years? What do you understand by the statement that a star is eight light years away from the Earth?
Stars at a distance of millions of kilometers from the earth. Thus, there large distance are expressed in the light year. One light year is the distance travelled in one year.
One light year = 9.46 x 1012 km.
If a star is located eight years away from the earth that means the distance between the star and the earth is equal to the distance which is travelled by light in eight years. So, the distance between the star and the earth us given by:
8 x (9.46 x 1012) km = 7.6 x 1012 km.
Describe with the help of a diagram an instrument which can be used to detect a charged body.
Sketch larynx and explain its function in your own words.
Arrange the following boxes in proper order to make a flow chart of sugarcane crop production.
Make a labelled diagram of a candle flame.
What is metamorphosis? Give examples.
The following Table shows the total power shortage in India from 1991– 1997. Show the data in the form of a graph. Plot shortage percentage for the years on the Y-axis and the year on the X-axis.
Make sketches of animal and plant cells. State three differences between them.
What is a constellation? Name any two constellations.
Describe the construction of a kaleidoscope.
Complete the crossword with the help of clues given below:
Across
1. This is necessary for photosynthesis.
3. Term for component present in the cytoplasm.
6. The living substance in the cell.
8. Units of inheritance present on the chromosomes.
Down
1. Green plastids.
2. Formed by collection of tissues.
4. It separates the contents of the cell from the surrounding medium.
5. Empty structure in the cytoplasm.
7. A group of cells.
(a) Find out the position of the image of an object situated at A in the plane mirror (Fig. 16.21).
(b) Can Paheli at B see this image?
(c) Can Boojho at C see this image?
(d) When Paheli moves from B to C, where does the image of A move?
What are sex hormones? Why are they named so? State their function.
What are the major groups of microorganisms?
Lightning and thunder take place in the sky at the same time and at the same distance from us. Lightning is seen earlier and thunder is heard later. Can you explain?
Match items in column A with those in column B.
A B
(i) Kharif crops (a) Food for cattle
(ii) Rabi crops (b) Urea and super phosphate
(iii) Chemical fertilisers (c) Animal excreta, cow dung urine and plant waste
(iv) Organic manure (d) Wheat, gram, pea
(e) Paddy and maize
What are the different ways in which water gets contaminated ?
Where are chromosomes found in a cell? State their function.
Explain why chloroplasts are found only in plant cells?
Make a sketch of the human nerve cell. What function do nerve cells perform?
Explain how CO2 is able to control fires.