naphthalene is a non polar substance so it will dissolve in non poalr solvent and camphor pon the other hand will dissolve in polar solvent.what do mean by polar here...???

Camphor is polar because it contans ketone in its structure which makes it polar(due to the lone pairs of electrons present on oxygen).Whereas in case of naphthalene C - H atoms show an electronegativity difference of 0.4, thus this is treated as slightly polar bond. But concerning the structure of naphtalene (two benzene rings), it is a very stable molecule and won't dissolve easily in water - thus it behaves mostly unpolar.