Geography L-2 Globe - latitudes and longitudes Notes

L-2 Globe - Latitudes and Longitude    

Define :-

1. Great circle - Any two opposite longitudes when joined together form a great circle. This marks the shortest distance between two places.
2. Local time - All places located on the same meridian have noon at the same time. This is the local time for that meridian.
3. AM and PM- Am stands for ante-meridian meaning before noon. PM stand for post meridian meaning afternoon.
4. IST - Indian Standard Time is the time accepted as the standard time for entire country. India is located to the east of Greenwich so the IST is five and a half hours ahead of GMT.
5. International date line (IDL)- It is the imaginary line which roughly passes the 180° longitude through the middle of Pacific Ocean. We add a day if we cross from west to east and  subtract if we cross east to west.

Question answers

Q. 1 Differentiate between the parallels of latitude and the meridians of longitude.

Ans - 

	Parallels of Latitudes	Meridians of Longitudes
1.	Imaginary horizontal lines from east to west of the earth.	Imaginary vertical lines from North Pole to South pole.
2.	The circles of latitudes are full circles	The meridians of longitudes are semicircles.
3.	There are 180 latitudes. 90 above the equator and 90 below.	There are 360 longitudes. 180 east of Prime Meridian and 180 in the west.
4.	They are of varied length.	They are all of the same length.
5.	They do not meet anywhere and run parallel to each other.	They are not parallel and meet at the poles.
6.	They help us to know about the temperature of various places.	They help us to know about the time zones of various places.
7	The places lying on the same parallel have different local time.	The places lying on the same meridians have same local time.

Q. 2 Draw a labelled diagram to show the heat zones of the earth.

Ans - 

Q.3 Give reason:

 a) Why there is need for standard time?

Ans - At times several meridians pass through a country. If places on each meridian were to follow their own local time, it would be difficult to prepare a common railway or airline timetable. To avoid such confusion each country follows the standard time which is the time of central meridian passing through that country.

b) Why Sun rises at Delhi before it rises at London?

Ans - Sun rises at Delhi before London because Delhi is on the east of greenwich meridian. Since our Earth rotates from west to east places on the east of Greenwich are ahead of the Greenwich Time(GMT), and those to the west of Greenwich are behind the GMT.

c) Why different countries have more than one time zones?

Ans - Some countries which have great east-west extent have several time zones. e.g. USA has 5 and Russia has 11. Hence such countries are divided into several time zones, each with its own standard time.

Q.4  How to calculate time of the places located at different meridians?

Ans - Places located on different meridians have different local times. 

•  The Earth takes 24 hours to complete 1 rotation i.e. to cover 360° of longitude.
  For 1 degree of longitude it takes:
  24 x 60         = 4 minutes 
•    360

• So it takes 4 minutes to cover 1° of longitude. 
• Places in the east are ahead in time than places in the west. 
• To calculate a degree of longitude towards east add 4 minutes 
• To calculate a degree of longitude towards west subtract 4 minutes
  For Example:
  Suppose it is 12 noon at Greenwich (0° ), what will be the time at 15°  E and 15°  W longitudes?
  Solution:
  The time difference between 0° and 15° = 15 x 4 = 60 minutes 
• At15° E, it will be 13 hours (12 +1)or 1pm 
• At15° W, it will be 11 hours (12-1) or 11 am
  

Q.5 What is relative location and absolute location?

Ans - Relative location: locating any place on Earth’s surface in relation to another place or nearby landmark is called the relative location eg. Rita’s house is to the west of Evergreen Gardens
Absolute location: locating a place with a coordinate system formed by latitudes and longitudes. For eg. Dhaka is located on 23°42’ North latitude 

Q.6. When it is 10 am in India, what is the time in Tehran (51 1⁄2 °E)?
Ans - Difference of longitude is 82.5 – 51.5 = 31°
1° longitude has a time difference of 4 minutes
4 x 31 minutes = 2 hours and 04 mins.
Tehran is situated west of Indian; 2 hours 04 minutes should be subtracted to from the Indian time.The time at Tehran is10hrs - 2hrs 04 minutes= 7 hours 56 minutes 

Q.7 Your friend lives in New York. She wants to watch a TV show, which will be telecast at 1:00 PM at Greenwich. At what time does she need to switch on her TV? (Hint - New York 74° W)

Ans - Difference of longitude is  between Greenwich and New York 0° + 74° = 74°

1° longitude has a time difference of 4 minutes
4 x 74 minutes = 4 hours and 56 mins.
New York is situated west of Greenwich; 4 hours and 56 mins. should be subtracted from the Greenwich time.

The time at which she will switch on her TV is1PM - 4hrs 56 minutes= 8:04AM