Physics

Q. A thin lens of focal length +12cm and refractive index 1.5 is immersed in water (refractive index =1.33).What is its new focal length

Q. If a thin lens is dipped in water, does its focal length change?

Q. Which colour of light has the shorter wavelength − red or violet?

Q. What is optical medium?
What ate its kinds?

Q. If the absolute refractive index of Glass is 1.5 and that of water is 4/3 find the refractive index of water with respect to glass

Q. A concave mirror has a focal length of $20cm$. The distance between the two positions of the object for which the image size is double of the object size is

1. $20cm$
2. $40cm$
3. $60cm$
4. $30cm$

Q. A man has a shaving mirror of focal length $0.2m$. How far should be held from his face in order to give an image of two fold magnification ?

Q. A concave mirror produces a real image twice the size of the object when placed at a distance of 22.5 cm from it. Where should be object be placed so that the size of the image becomes three times that of the object?

1. 20 cm
2. 22.5 cm
3. 24 cm
4. 30.4 cm

Q. Two plane mirrors are at right angles to each other. A man stands between them and combs his hair with his right hand. In how many of the images will he be seen using his right hand :

1. Zero
2. $1$
3. $2$
4. $3$

Q. Draw a ray diagram to show the formation of image by a concave mirror for an object placed between its pole and focus. State three characteristics of the image.