Q1.
Repeat Activity 12.2 but replace the torch with an electric lamp. Then place the globe at different positions on a circle around the lamp while maintaining the tilt of the globe. (i) Note down your observations regarding how much of the Northern and Southern hemispheres of the globe are illuminated at different positions. (ii) Rotate the globe and take a note of the length of the day and night on different parts of the globe. (iii) Repeat (ii) for different positions of globe on the circle.
Answer
This project turns the whole chapter into one table-top model. The one rule that must never be broken: the globe's axis must keep pointing in the same direction — the same way, towards the same corner of the room — at every position on the circle. Do not turn the stand to face the lamp.
How to set it up
- Stand a bare electric lamp (no shade) in the middle of a table in a dark room. This is the Sun.
- Chalk a circle of radius about 60–75 cm around the lamp. Mark four positions on it: June, September, December, March.
- Carry the globe around the circle, keeping the axis tilted the same way throughout, and stop at each mark.
(i) How much of each hemisphere is lit
| Position | Northern Hemisphere | Southern Hemisphere | Poles |
|---|---|---|---|
| June | More than half of it is lit | Less than half of it is lit | North Pole fully lit; South Pole fully dark |
| September | Exactly half | Exactly half | The lit–dark line passes through both poles |
| December | Less than half of it is lit | More than half of it is lit | North Pole fully dark; South Pole fully lit |
| March | Exactly half | Exactly half | The lit–dark line passes through both poles |
(ii) and (iii) Length of day and night — at each position, spin the globe slowly and watch a sticker on Delhi, one on the equator and one on Australia. Count roughly what fraction of each turn the sticker spends in the light.
| Place on the globe | June position | March / September | December position |
|---|---|---|---|
| Delhi (Northern Hemisphere) | Day longer than night | Day ≈ night | Day shorter than night |
| On the equator | Day ≈ night | Day ≈ night | Day ≈ night |
| Australia (Southern Hemisphere) | Day shorter than night | Day ≈ night | Day longer than night |
| North Pole | 24 hours of day | On the boundary | 24 hours of night |
What the model proves: the lamp never changed and the distance never changed — only the direction of the tilt with respect to the lamp changed. That alone produced longer days, shorter days and midnight sun. This is the strongest possible demonstration that the seasons come from the tilt, not from the distance.
Tip: use a lamp without a shade so light spreads in all directions, and keep the room really dark. Take a photograph of the globe at each position — the four pictures side by side make an excellent chart for the class.