GEOGRAPHY STD 9 Geographic Grid -Latitudes and Longitudes 2018-2019 Q1. Define Geographic Grid. The network of latitudes and longitudes are known as Geographic Grid. They help us to locate places on the surface of the earth. Q2. Give the most important characteristics of lines of latitudes Latitude is the angular distance of a place north or south of the Equator. There are 180 parallels of latitudes apart from the Equator. Each parallel of latitude is a circle. Only the Equator is a Great Circle, all the rest of the latitudes decrease in size as we move towards the poles. The distance between two latitudes is always equal. They help us to determine the climate of a place. Q3. Name the main latitudes. The five major circles of latitude are, from north to south: The Arctic Circle (66 N) It is the place where the sun never sets on 21 st June. Beyond this place we have six months of days and six months of night. The Tropic of Cancer (23 N) It is highest limit in the northern hemisphere which receives the direct rays of the sun 21 st June. The Equator (0 latitude) it is the middle of the earth where the sun shines directly throughout the year. The Tropic of Capricorn (23 S) It is highest limit in the southern hemisphere which receives the direct rays of the sun on 22 nd December. The Antarctic Circle (66 S) It is the place where the sun never sets on 22 nd December. Beyond this place we have six months of days and six months of night. Other than these the North Pole and the south poles are latitudes which are just dots and are situated at an angular distance of 90 degrees to the north or south of the Equator. Q4. Show how the angular distance between the latitudes are 111 km. The circumference of the earth (ie. 360 ) is 40,077 km. thus 1degree is 40,077 360 = 111km. Q5. What are various uses of latitudes? i) They help us to locate places with the help of longitudes and calculate the distance between two places. ii) Latitudes also help us to determine the climate of a place. iii) Vegetation, animal life and human life of a place.
Q6. What are the characteristics of Torrid Zone, Temperate zone and Frigid zone? Torrid Zone: 0-23½ N/S i) Hottest zone ii) Sun is overhead twice in tis zone iii) Widest of the five zones iv) Length of day is practically same throughout the year. v) Very little difference between summer and winter vi) Also known as low latitudes. Temperate zone:23½ 66½ N/S i) Zone of moderate temperature ii) Great difference between summer and winter temperature iii) Sun never overhead. Receives only slanting rays of the sun. iv) Most people live in this zone for cool climate. v) Also known as mid latitudes. Frigid Zone: 66½ 90 N/S i) Coldest zone because it is slanting to very slanting rays that reach these places. ii) It experiences 6 months of days and six months of night. iii) Also known as high latitudes. Q7. What are Longitudes? It is the angular distance of a place east or west of the prime meridian.
Q8. State the main characteristics of meridians of Longitudes. Q8. What is the meridian of Greenwich also known as? Meridian of Greenwich is also called the Prime Meridian. It is 0 degree. Q9. What is 180 longitude called? It is called the international dateline. Q10. What is the reference line for measuring longitudes? It is the prime meridian. Q11. Explain why the lines of longitude are called meridians of longitude? It is because the word meridian or Latin meridianum means noon and all places along the same meridian experiences noon at the same time. Q 12. The distance between two parallels of latitudes is equal to about 111km., but the distance between two consecutive meridians of longitude is equal to 111km only at the equator. State why is it so? The distance between two consecutive meridians of longitude diminishes as we move towards the poles as the longitudes converge at the poles, however latitudes are equidistant.
Q13. How is longitude related to time? The earth rotates from west to east through the 360 in 24hours. The sun appears to move from east to west at the speed of 1 in 4 minutes. i.e.1440 minutes/360.thus 15 are covered in 60 minutes or 1hour. Q14. What is Great Circle? A great circle is any circle that divides the sphere (Earth) into two halves and it is also the centre of the sphere (Earth). Q15. Why are meridians of Longitudes all great circles? All meridians of Longitudes are great circles because they along with the opposite longitude divide the earth into two equal halves. Q16. Why no other latitudes are great circles other than the Equator? This is because it is only the Equator that divides the earth into two equal parts but all other parallels of latitudes are smaller circles. Q17. What is the advantage of following the great circle route? The great circle route is the shortest distance between two places on earth as it lies on the arc of a circle. This is best for the places located on the opposite sides of the globe. Q18.Why cannot the sailors always take the great circle route? This is because: It can take them to dangerous waters or it may take them through areas when ice is present and this is unsafe for navigation. Q19.Give reasons: a) The time difference between India and London is 5hrs. 30 mins. The longitude of London is 0 The longitude of India is 82 30 E For a longitudinal difference of 1 the time difference is 4mins So for longitudinal difference of 82½ the time difference is 4 82½ Or 4 165/2 or 330mins. Or 330/ 60 = 5hrs.30 mins. b) The 0 meridian is known as the Prime Meridian. It is called the Prime Meridian because it is the reference line for measuring east west distance. c) International Date line is not a straight line, coinciding with longitude 180.
International Date Line is not a straight line and does not coincide with the longitude 180, so as to avoid landmasses, allowing it to pass only over the waterbodies to avoid confusion in day and date. d) Countries like USA, Canada or Russia have more than one time zone. Why is it so? If the longitudinal extent of the country is very vast, then they do not have a single Standard time for the entire country. In such cases there is a time zone covering 15 of longitude. Longitudes can be at a minimum interval of 7½ longitudes. e) Local time differs from place to place. Local time at a place is fixed with the reference to the path of the sun in the sky. Local time differs from place to place because of variations in longitudes. A difference of longitude of 1 there is a time difference of 4mins. Q20. What is the difference between standard time and local time? The standard time is calculated on the basis of the central meridian of the country, or the meridian passing over the most important city. The time of the central meridian is followed by the time zone consisting of 15 span of longitudes, whereas the Local time at a place is fixed with the reference to the path of the sun in the sky. It is not followed by the time zone as it varies from meridian to meridian. Q21. What is the International Date Line? Mention two places where the International Date Line deviates from the 180 longitude. The International Date Line is the 180 E and West line. This longitude is diametrically opposite to that of the Greenwich Meridian. It is not straight, but zigzags to avoid land masses. It passes only through water bodies. It marks the place on the earth s surface where each new date first begins. The International Date Line curves east of 180 in Bering Strait between Siberia and Alaska. It avoids the Hawaiian, Fiji, Tonga Islands. Q22. What is meant by Greenwich Mean Time? Greenwich Mean Time (G.M.T.) is also known as Universal Time. It is the Time measured from Greenwich situated on 0 longitude and is used as a standard for reference all over the world. Q23. What is meant by Indian Standard Time (I.S.T)? I.S.T. is the Indian Standard Time. IT is the time that is measured from Allahabad situated on 82½ (82-30 minutes) longitude and is used as a standard for the entire country. Q24. Distinguish between:
(a) Equator and Prime Meridian. Equator 1. The Equator is a reference line used for measuring distances to the North and South Prime Meridian The Greenwich or Prime Meridian is the reference line for measuring East-West distances. It converges on the two poles. (b) Great Circle and Small Circle. Great Circle 1. They divide the earth into two halves and are also the centre of the earth 2. The radius of the Great circle is the same as the radius of the earth Small Circle The centres of the small circles are points other than the centre of the earth The small circles have radius which are smaller than that of the earth. Q25. Give reasons for the following: (i) Which is the greater circle of latitude 10 N or 60 N? Why? The 10 N is a greater circle of latitude because latitudes are parallel to each other and as we go away from the Equator they get smaller until they are a point at 90 N/S and 10 N is closer to the equator than 60 N. (ii) The lines of longitude are of equal length. All lines of longitude are of equal length because every longitude is a great circle and divides the earth into two equal halves and it is also the centre of the earth. (iii) A person travelling from Mumbai to London alters the time on his watch at several places. The person alters his watch many times because the East to West or longitudinal extent is very great. Hence he has to cross many longitudes and times zones. So, for every longitude he crosses there is a time difference of 4 minutes, and for every time zone he crosses, the difference is one hour. Hence, as he is going to London, he crosses 5½ time zones. So the difference is 5½ hours. So he is behind time. (iv) The sun rises at a difference time at A (10 N, 15 E) than at B (10 N, 15 W). Also denote the position of any other place C at which the sun rises at the same time as at the place. The sun rises at A first, because A is 15 E, while B is 15 W. So A is ahead of time by 2 hours than B. Place C (15 N, 15 E) will have the same time as A.
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