An observer moves towards a stationary plane mirror at a speed of 4 ms–1. With what speed will his image move towards him?  


Correct option is

Since the distance of the image from the mirror is equal to the distance of the object (observer) from the mirror at each instant of time during his motion, the speed of his image with respect to him is 4 + 4 = 8 ms–1.



When a thin wedge-shaped film is illuminated by a parallel beam of light of wavelength 6000 Ã…, 7 fringes are observed in a certain region of the film. How many fringes will be observed in the same region of the film if light of wavelength 4200 Ã… is used?


A parallel beam of white light is reflected from a thin wedge-shaped film. The colour of the fringe at the edge of the wedge will be 


When a ray of light is incident on a glass slab at an angle of 60o, the angle between the reflected and refracted rays is 90o. The refractive index of glass is  


The polarising angle for glass is 


What is the SI unit of luminous intensity?


What are the dimensions of luminous intensity?   


What is the luminous intensity of a lamp which produces an illuminance of 12 lux at a distance of 5.0 m from it?  


To print a photograph from a negative, the time of exposure to light from a lamp placed 60  cm away is 2.5 s. What exposure time is required if the lamp is placed 1.2 m away?


A lamp placed at a distance of 50.0 cm from a screen on one side produces the same illumination as a standard 60 cd candle placed 100 cm away on the other side of the screen. What is the luminous intensity of the lamp?



Which mirror should be used to obtain a parallel beam of light from a small lamp?