A meter scale is held vertically in front of a plane mirror of length 15cm. A student peeps through a hole at 40cm mark. Sir you can refer to nso class 8th achiever section of 2014 question paper. The range of the scale of the meter ruler that can be seen? If the hole is at 80cm mark of the scale, then the range of the meter ruler that can be seen in mirror is?
For student's eye to see the range of the ruler i.e. the maximum reading and the minimum reading, the eye must look at the two extreme ends of the 15 cm mirror. Here, we use the fact that angle of incidence is equal to angle of reflection to show the range that can be seen by the eye through the mirror. If the student and the object is at the same perpendicular distance away from the mirror, the image seen through the mirror is twice as much as the size of the mirror. For this case a 15 cm mirror can see a range of 30 cm.