Question

(a) plane glass
(b) convex lens
(c) concave lens
When two plane mirrors are placed at an angle of 60° to each other, the images formed ar
When two plane mirrors are placed at an angle of 90° to each other, the images formed are :
(d) six
(a) three
(b) four
( (c) five
(d) six
Write T for true and F for false statements.
Deficiency of vitamin A may cause night blindness.
Lens focusses the light onto retina.
Each Braille character contains up to six dots.
Braille is the method of writing that blind people can understand.​

Answer 1

$\huge\rm { _!! Question !_! }$

When two plane mirrors are placed at an angle of 60° to each other, the images formed are:

$\huge\rm { _!! Answer !_! }$

${\underline {\underline {\boxed {\rm {\red { Five \: images}}}}}}$

$\rm { No. \: of \: images = \dfrac{ 360° }{ Angle \: b/w \: mirrors } -1}$

$\rm { No. \: of \: images \: formed = \cancel { \dfrac{ 360° }{ 60° }} -1 }$

$\rm { No. \: of \: images \: formed = 6-1= 5 images}$

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$\huge\rm { _!! Question !_! }$

When two plane mirrors are placed at an angle of 90° to each other, the images formed are :

$\huge\rm { _!! Answer !_! }$

${\underline {\underline {\boxed {\rm {\red { three \: images}}}}}}$

$\rm { No. \: of \: images = \dfrac{ 360° }{ Angle \: b/w \: mirrors } -1}$

$\rm { No. \: of \: images \: formed = \cancel { \dfrac{ 360° }{ 90° }} -1 }$

$\rm { No. \: of \: images \: formed = 4-1=3 images}$

_______________________________

Write true or false -:

• Deficiency of vitamin A may cause night blindness.

${\underline {\underline {\boxed {\rm {\green { True }}}}}}$

• Lens focusses the light onto retina.

${\underline {\underline {\boxed {\rm {\green { True }}}}}}$

• Each Braille character contains up to six dots.

${\underline {\underline {\boxed {\rm {\green { True }}}}}}$

• Braille is the method of writing that blind people can understand.

${\underline {\underline {\boxed {\rm {\green { True }}}}}}$

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