As doctors warn it can cause a dangerous reaction with a host of common drugs... 1  Researchers warn that grapefruit reacts with many medicines. 2  The fruit can cause devastating side-effects from stomach bleeding to kidney problems. 3  Doctors say the public is ignorant to the dangers and putting themselves needlessly at risk.
According to the definition of the question (based on light reflection and not light emission), a well-polished mirror is the the whitest substance on earth. The main reflection layer is usually made out of silver.
Alpha radiation is the weakest. It can be stopped by a piece of paper and posses no threat to any human tissue. Beta radiation is strong, but still not lethal. It can be stopped by most clothing or fabrics. Gamma radiation is the strongest. It can only be stopped by lead.