Maharashtra Board Class 7 Geography Chapter 1 How Seasons Occur Part 1 PDF Download

How Seasons Occur - Part 1

Let's Recall

How do day and night occur on the earth?

What term is used to describe the earth's revolution around the sun?

How long does the earth take to do so?

In which hemispheres is our country located?

Why don't the sun's rays fall perpendicular at all the places on the earth?

You must have noticed the change in the duration of daytime and the nighttime from 19th to 28th June. It takes 24 hours for the earth to rotate around itself. It rotates from west to east. The earth's rotation has enabled us to measure time in terms of days. During a single day, we experience different stages like sunrise, midday, sunset as well as daytime and nighttime.

To understand the changes in the locations of sunrise and sunset on the horizon, let us carry out the activity given on the next page.

Can You Tell?

How did you find out the duration of the night?

Which two dates had days and nights of the same duration?

With the help of the table, you saw how the duration of the day and the night changes. Do you think such a change occurs everywhere on the earth?

Use the following format to record the duration of daytime from the 19th to 28th of every month from September to December.

Note the timings of sunrise and sunset in your area, for the following period by direct observation, or using calendars, newspapers or the Internet. A specimen table has been given below. Record the entries for the month of June, find the answers to the following questions and discuss them.

Among the records in the table which is the longest day?

What difference do you notice in the duration of the nights day by day?

Guess the reason behind it.

Geographical Explanation

You must have noticed the change in the duration of daytime and the nighttime from 19th to 28th June. It takes 24 hours for the earth to rotate around itself. It rotates from west to east. The earth's rotation has enabled us to measure time in terms of days. During a single day, we experience different stages like sunrise, midday, sunset as well as daytime and nighttime.

To understand the changes in the locations of sunrise and sunset on the horizon, let us carry out the activity given on the next page.

Teacher's Note

Students need to observe the changes in sunrise and sunset times in their own place. This helps them understand why summer days are longer in India.

Exam Trick

Remember: The earth takes 24 hours to rotate once. This is how we get day and night. Write this in your exams - it is always asked!

Points to Remember

The earth rotates from west to east in 24 hours.

During one day, we see sunrise, midday, and sunset.

The duration of day and night changes throughout the year.

The position of sunrise and sunset changes on the horizon.

Try This

Paste a large white paper on one side of the table.

Place a torch in front of the table in such a way that it wouldn't move.

Stand a rod or a candle between the white paper and the torch. See Figure 1.1

Direct the light beam of the torch in such a way that the shadow of the rod or candle falls on the paper.

Mark the position of the shadow on the paper.

Move the table along with the rod or candle, from one side to the other slowly.

Observe and mark the position of the shadow that falls on the paper.

Note the change in the location of the shadow.

Geographical Explanation

From this activity, you will realize that as the position of the table changes, the position of the shadow also changes. If the positions of the sunrise and the sunset on the horizon are observed for the whole year, you will realize that they keep on changing. Let us try to understand the reason behind this with the help of the next activity.

Teacher's Note

This shadow experiment shows how the sun's position changes in the sky. Just like shadows move in the afternoon, the sunrise point also moves slowly throughout the year.

Exam Trick

Remember: The shadow moves because the light source moves. In the same way, sunrise and sunset points move because the earth's position changes.

Points to Remember

The shadow position changes when the light source moves.

Sunrise and sunset positions change throughout the year.

We can observe this change by watching the sky.

Try This

Keeping some distance, fix the stick near a wall that receives sunlight at the time of sunrise or sunset throughout the year. Remember that the stick has to be fixed at this spot for a period of about one year.

After the observation, mark the position of the shadow for that date.

If the position of the shadow changes, measure and note the distance between the earlier and the changed position.

During the period of this activity, observe the place of sunrise and the sunset on the horizon as well.

The next part of the lesson should be dealt with in the month of September.

Study the duration of daytime and nighttime on the basis of observations from the table for the month of September.

What was the direction of the shadow of the stick in the month of September?

On which day was the duration of the day and the night the same?

For teachers: This activity is to be conducted throughout the year. Start this within eight days after the school opens. Continue it till the end of December. Make observations once in a week at the time of sunrise or sunset as per your convenience.

Take a thick stick about 1.5 to 1.7 m long.

Think About It

If the position of the shadow on the wall moves towards the north, in which direction does the location of sunrise or sunset appear to shift?

Teacher's Note

This year-long activity helps students understand seasonal changes in India. By observing stick shadows, they learn why summer days are longer and winter days are shorter.

Exam Trick

Remember: When shadows move north, sunrise and sunset positions also move. This happens because the earth's position relative to the sun changes throughout the year.

Points to Remember

Shadows move as the sun's position changes in the sky.

We must observe and record shadow positions for one full year.

The shadow direction tells us about seasonal changes.

In September, day and night have equal duration.

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