Geometric/arithmetic question (1 Viewer)

kpad5991

Member
Joined
Dec 29, 2016
Messages
238
Gender
Male
HSC
2018
When light passes through one sheet of very thin glass, it's intensity is reduced by 3%. What is the minimum number of sheets that will reduce the intensity of the light below 1%?

What is the first, second and third term?
Is this a geometric or arithmetic progression ?
 

braintic

Well-Known Member
Joined
Jan 20, 2011
Messages
2,137
Gender
Undisclosed
HSC
N/A
When light passes through one sheet of very thin glass, it's intensity is reduced by 3%. What is the minimum number of sheets that will reduce the intensity of the light below 1%?

What is the first, second and third term?
Is this a geometric or arithmetic progression ?
For a start, this is 2 unit, not 4.

97% of the light gets through the first sheet.
97% of THAT transmitted light gets through the second sheet. So 0.97^2 of the light incident on the first sheet gets through the two sheets.
Following this through, if there are n sheets then the fraction of light which gets through is 0.97^n.
So you need to solve 0.97^n < 0.01
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top