\"Photo-gray\" lenses for eyeglasses darken in bright sunshine because the lense

Question

"Photo-gray" lenses for eyeglasses darken in bright sunshine because the lenses contain tiny, transparent AgCl crystals. Exposure to light removes electrons from Cl- ions, forming a chlorine ato in an excited state (Indicated below by the asterisk):

Cl- -----> Cl* + e-

The electrons are transferred to Ag+ ions, forming silver metal:

Ag+ + e- -----> Ag

Silver metal is reflective, producing the photo-gray color. How might substitution of AgBr for AgCl affect the light sensitivity of photo-gray lenses? In answering this question, consider whether more or less energy is needed to remove and electron from a Br- ion than from a Cl- ion.

Explanation / Answer

ANSWER

Less energy will be required to remove an electron from Br- than Cl- (Because electron affinity of Cl- is greater than Br-). Hence the electrons will be released easily, as a result Ag+ ion will be reduced to Ag more effectively . This will result in INCREASED SENSITIVIT OF THE Lense.

Related Questions

Navigate

• Browse (All)
• Browse #
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.