Final answer:
The image formed by a lamp placed in front of a converging lens and reflected by a plane mirror would appear 25 cm behind the lens. To see the back of your head, two angled mirrors are required. option 2 is correct
Step-by-step explanation:
option 2 is correct The student's question relates to the concept of geometrical optics, specifically the behavior of images formed by lenses and mirrors. When a lamp of height 5 cm is placed 40 cm in front of a converging lens with a focal length of 20 cm, according to the lens formula (1/f = 1/v - 1/u), where u is the object distance and v is the image distance from the lens, we can calculate the image's position.
The image would be formed 40 cm behind the lens, which would then be reflected by the plane mirror 15 cm behind the lens. Observing the system from the front, the image would appear 25 cm behind the lens due to the mirror's reflection. To see an image of the back of your head, the minimum number of mirrors required is two, positioned at an angle to each other, allowing you to see the reflection of the back of your head as per Figure 25.48.
When backing up under a trailer, you should line up your right mirror along the right edge of the trailer. This will allow you to see the trailer and ensure that you are aligned correctly. Lining up directly in front of the trailer may not provide the best perspective and could result in improper positioning.