CBSE Class 10 Science 2017 · Paper 531/1 · Question 34

Light - Reflection and Refraction 2 marks Medium

Study the following ray diagram and state any two mistakes committed by the student while tracing it. Rectify these mistakes and draw the correct ray diagram to show the real position of the image corresponding to the position of the object.

Answer

The foci were unequally spaced and a ray missed O; correctly drawn, the image is real, inverted, enlarged and beyond $2 F_{2}$ .

Mistakes (any two): (i) The foci are marked at unequal distances:

F_{2}

is nearer the lens than

F_{1}

, and

2 F_{1}

and

2 F_{2}

are not at equal distances either; both foci of a lens lie at the same distance

f

from the optical centre. (ii) The ray drawn towards the optical centre does not pass through

O

: it crosses the principal axis to the right of

O

, whereas a ray through

O

goes straight on. (iii) The image is shown between

F_{2}

and

2 F_{2}

and smaller than the object; for an object between

F_{1}

and

2 F_{1}

it must be beyond

2 F_{2}

and enlarged. Correct ray diagram (see the figure): with

O F_{1} = O F_{2} = f

, the ray parallel to the axis passes through

F_{2}

after refraction and the ray through

O

goes undeviated; they meet beyond

2 F_{2}

, where the image is real, inverted and enlarged.

🔒 Step-by-step solution

CBSE Class 10 Science 2017 · Paper 531/1 · Question 34

Answer

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