A driveway is illuminated at night by identical lamps at the top of two poles 30 ft high and 40 ft apart. Assuming the lamps radiate equally in all directions, compare the illumi- nance at ground level for points directly under one lamp and midway between them.

Step 1 of 3

Step 1 of 3Solution:

Step 1 of 3Solution:Height of two poles is 

Step 1 of 3Solution:Height of two poles is Distance between two poles is 

Step 1 of 3Solution:Height of two poles is Distance between two poles is It is given that there are two identical lamps at the top of two poles which radiate equally in all directions. Thus powers of the two lamps are equal then.

Step 1 of 3Solution:Height of two poles is Distance between two poles is It is given that there are two identical lamps at the top of two poles which radiate equally in all directions. Thus powers of the two lamps are equal then.Now illuminance of two lamps at a point at ground level directly below one lamp is

Step 1 of 3Solution:Height of two poles is Distance between two poles is It is given that there are two identical lamps at the top of two poles which radiate equally in all directions. Thus powers of the two lamps are equal then.Now illuminance of two lamps at a point at ground level directly below one lamp is

Step 1 of 3Solution:Height of two poles is Distance between two poles is It is given that there are two identical lamps at the top of two poles which radiate equally in all directions. Thus powers of the two lamps are equal then.Now illuminance of two lamps at a point at ground level directly below one lamp isNow illuminance of two lamps at a point at ground level which is midways between two poles is

Step 1 of 3Solution:Height of two poles is Distance between two poles is It is given that there are two identical lamps at the top of two poles which radiate equally in all directions. Thus powers of the two lamps are equal then.Now illuminance of two lamps at a point at ground level directly below one lamp isNow illuminance of two lamps at a point at ground level which is midways between two poles is