26 .   A   s t u d e n t   f o c u s e s   t h e   i m a g e   o f a   c a n d l e   f l a m e .   p l a c e d   a t   a b o u t   2   f r o m   a   c o n v e x   l e n s e   o f   f o c a l   l e n g t h   10   c m   ,   o n   a   s c r e e n .   A f t e r   t h a t   h e   g r a d u a l l y   m o v e s   t h e   f l a m e   t o w a r d s   t h e   l e n s   a n d   e a c h   t i m e   f o c u s e s   i t s   i a g e   o n   t h e   s c r e e n .     ( a )   I n   w h i c h   d i r e c t i o n   d o e s   h e   m o v e   t h e   l e n s   t o   f o c u s   t h e   f l a m e   o n   t h e   s c r e e n ?     ( b )   W h a t   h a p p e n s   t o   t h e   s i z e   o f   t h e   i m a g e   o f   t h e   f l a m e   f o r m e d   o n   t h e   s c r e e n ?     ( c )   W h a t   d i f f e r e n c e   i s   s e e n   i n   t h e   i n t e n s i t y   ( b r i g h t n e s s )   o f   t h e   i m a g e   o f   t h e   f l a m e   o n   t h e   s c r e e n ?     ( d )   W h a t   i s   s e e n   o n   t h e   s c r e e n   w h e n   t h e   f l a m e   i s   v e r y   c l o s e   ( a t   a b o u t   35   c m )   t o   t h e   l e n s ?  

Dear Student,

(a)As the candle is moved towards the lens, the image distance increases. Thus, 
the student moves the lens away from the screen to focus the image.
(b)The size of the image increases when the object is moved towards the lens.
(c) Intensity decreases.
(d)When the candle is moved very close to the lens, no image is formed on the screen. A virtual image is formed behind the candle on the same side of the screen.

Regards,

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