Two wires forming the open ends of a circuit consisting of a bulb and an electric cell are dipped in the following liquids one by one and it is noted whether the bulb in the circuit glows or not. Following are the observations :

A convex lens forms an image of an object placed 30 cm away. The image is formed at 60 cm on the other side. The magnification is:

Which of the following statements is correct about the absolute refractive index?

Which of the following is NOT correct according to the sign convention for spherical lenses?

An object is placed 15 cm in front of a convex lens of focal length 25 cm. The image distance will be