One of the following does not apply to a concave mirror. This is : (a) focal length is negative (b) image distance can be positive or negative (c) image distance is always positive (d) height of image can be positive or negative
Only one of the following applies to a concave lens. This is : (a) focal length is positive (b) image distance can be positive or negative (c) height of image can be positive or negative (d) image distance is always negative
The enthalpies of elements in their standard states are taken as zero. The enthalpy of formation of a compound (a) is always negative (b) is always positive (c) may be positive or negative (d) is never negative
Why proton is always positive charge