BASICS OF GEOGRAPHY
LATITITUDES
Temperature will be more @ A1 than A2 due to slantness.
Increase in slantness of sun rays leads to decrease in ANGLE OF INCIDENCE (AOI) HENCE decrease in temp.
- All the parallel circles from the equator .
- The angle b/w center of earth and equatorial plane is called latitudinal angle.
- The circle or line joins the point having the same latitudinal angle called latitudinal angle called Latitudes. + Radius decreases from 0⁰ towards 90⁰ + Distance b/w two Latitudes is approx 111km + They play an important role in indicating the temperature of the region + Latitudes are horizontal lines that imagined on the earth.
LONGITUDES
Are Imaginary lines which join N pole to S pole + the degree of each longitude signifies the angle of distance from PM. + The distance b/w 2 longitudes is more @ equator and lesser @ poles. + means 111 km at 0⁰ only + plays an important role in deciding the time of a place.
Standard and local time
Q. If the local time as a place having a longitude of 45⁰ w is 6 AM then what time will the time be at 60⁰ E?
Local Time
- Local time of a place is determined by the position of the Sun over that place’s longitude.
- When the Sun is at its highest point in the sky (culmination), it is considered 12:00 Noon at that location.
- Every 15° of longitude equals 1 hour of time difference (Earth rotates 360° in 24 hours).
Standard Time
- Standard Time is the local time of a specific standard meridian chosen by a country.
- This meridian is usually selected to be roughly in the middle of the country.
- It helps maintain uniform time across the country, especially in countries with wide longitudinal extent.
- Standard meridians are ideally multiples of 15° longitude to match international time zones.
India’s Standard Time (IST)
Standard Meridian of India: 82.5° E (passes near Mirzapur, Uttar Pradesh).
IST is +5 hours 30 minutes ahead of Greenwich Mean Time (GMT).
Example: If it’s 12:00 noon GMT, it is 5:30 PM IST.
4. Rotation
The Earth's axis is tilted at an angle of 23 ½ ⁰ from the normal, as we can say that earth's axis makes an angle of 66 ½ ⁰ from the orbital plane.
● Milankovitch cycle :- the tilt of earth's axis is not fixed to 23 ½ it changes from 21 ½ to 24 ½ in the span of almost 41000 years.
5. REVOLUTION
Effect of Earth’s Tilt and Revolution on Sun’s Vertical Rays
Due to the tilt of Earth's axis (23.5°) and its revolution around the Sun, the vertical (direct) rays of the Sun shift north and south throughout the year.
This apparent movement of the Sun is between the Tropic of Cancer (23.5° N) and the Tropic of Capricorn (23.5° S).
As a result, the Sun is directly overhead at different latitudes during different times of the year.
High Insolation in the Tropics
The vertical rays of the Sun deliver maximum unit per area
These rays fall most directly in the tropical zone (between the Tropic of Cancer and Tropic of Capricorn).
Hence, this region receives high insolation and is called the torrid or tropical zone.
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FIG : MOVEMENT OF EARTH OVER THE YEARS