An objects is placed 4cm in front of a concave mirror. Thevirtual image is 2cm f
ID: 1678220 • Letter: A
Question
An objects is placed 4cm in front of a concave mirror. Thevirtual image is 2cm further from the mirror when the mirror isconcave than when it is planar. Find the focal length of theconcave mirror. I used the 1/f = 1/o + 1/i = 1/4cm + 1/2cm but that waswrong ans choices -8cm +8cm + 24/5 +12 quest 2 Two identical polaroid sheets are oriented at an angleby angle theta with respect to their transmission axes. The valueof theta that permits only 12.5% of initially unpolarized lighhtthrough both sheets is ans choices 30 60 25 76 45 An objects is placed 4cm in front of a concave mirror. Thevirtual image is 2cm further from the mirror when the mirror isconcave than when it is planar. Find the focal length of theconcave mirror. I used the 1/f = 1/o + 1/i = 1/4cm + 1/2cm but that waswrong ans choices -8cm +8cm + 24/5 +12 quest 2 Two identical polaroid sheets are oriented at an angleby angle theta with respect to their transmission axes. The valueof theta that permits only 12.5% of initially unpolarized lighhtthrough both sheets is ans choices 30 60 25 76 45Explanation / Answer
Distance of the object u = -4 cm
Distance of the image when the mirror is planer is v= 4cm
Distance of the image when the mirror is concave is v ‘ = 4 cm +2 cm = 6 cm
From the relation ( 1/ u ) + ( 1/ v ‘ ) = ( 1/ f)
( 1/ 4) + ( 1/ -6 ) =( 1/ f)
0.08333 = ( 1/f)
From this focal length f= 12 cm
(b). Intensity of the light after 1 st sheet I = Io/2