For finding the focal length of a convex lens by obtaining the image of a distant object, one should use as the object

Following signs are usually shown on the bottles of commercial acetic acid. The symbols indicate respectively that acetic acid is:

To find the focal length of a concave mirror Rahul focuses a distant object with this mirror. The chosen object should be

Four student A, B, C and D traced the paths of incident ray and the emergent ray by fixing pains P and Q for incident ray and pains R and S for emergent ray for a ray of light passing through a glass slab.

The correct emergent ray was traced by the student:

To show that zinc is a more active metal than copper, the correct procedure is to