Download App

MODEL PAPER 1 — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10ScienceMODEL PAPER 15 Marks
Question
What is lens formula? Give its sign conventions and assumptions.
✓

Answer

If u is the distance of object and v, the distance of image from optical centre of the lens, then focal length fis related to u and v by $\frac{1}{f}=\frac{1}{v}-\frac{1}{u}$ which is called lens formula. The formula is equally applicable t to convex, concave or any other type of lens. (e.g. concavo-convex, plano-convex, convexo-concave, plano-concave etc.)
Sign Conventions:
(1) The object is always placed to the left of the lens.
(2) All distances parallel to principal axis are measured from optical centre of the lens.
(3) All distance measured to the right of optical centre (along x-axis) are taken as positive while those measured to the left of optical centre (along x-axis) are taken as negative.
(4) Distance measured perpendicular to and above the principal axis (along y axis) are taken as positive.
(5) Distance measure perpendicular to and below the principal axis (y'-axis) are taken as negative.
Assumptions (1) Object is taken on principal axis. (2) The lens is thin.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "[5 marks Questions]" from MODEL PAPER 1→MODEL PAPER 1 — all question types→Science STD 10 question papers→CBSE Board STD 10 question papers→CBSE Board question paper generator→

Similar questions

Give the structural differences between saturated and unsaturated hydrocarbons with two examples, each.
→
Explain the difference between each of the following pairs of terms:
  1. Receptor and effector.
  2. Cerebrum and cerebellum.
→
A man bought a device X which could cook pulses, vegetables and rice without using any fuel like wood, coal, kerosene or LPG, etc. This device did not work at night. It also took a lot of time for cooking.
  1. Name the device X.
  2. What is the source of energy which cooks food in this device?
  3. What is the name of the process which traps energy in this device?
  4. State one advantage (other than saving on fuel) or using such a device for cooking food.
→
Draw a labelled circuit diagram of a simple electric motor and explain its working. In what way these simple electric motors are diffferent from commercial motors?
→
What are non-renewable sources of energy? Give two examples of such sources.
→
How does fertilisation take place? Fertilisation occurs once in a month. Comment.
→
Explain why, though both a plane mirror and a sheet of paper reflect light but we can see the image of our face in a plane mirror but not in a sheet of paper.
→
Esters are When ester treated with an alkali, the reaction gives ethanol and sodium ethanoate. This reaction is called saponification reaction because this reaction forms the basis of preparation of soap. This can be given by following equation.
→
Match Column I with Column II.
  Column I   Column II
(i) $\text{H}_2(\text{g})\ +\ \text{S(l)}\xrightarrow{\ (\text{boiling})\ \ }\text{H}_2\text{S(g)}$ (A) Dispacement reaction.
(ii) $\text{Zn}\ +\ 2\text{HCl}\ \xrightarrow{\ \ \ \ \ \ \ \ }\text{ZnCl}_2\ +\ \text{H}$ (B) Neutralisation reaction.
(iii) $\text{2NaOH}\ +\ \text{H}_2\text{SO}_4\ \xrightarrow{\ \ \ \ \ \ \ \ \ \ }\text{Na}_2\text{SO}_4\ +\ 2\text{H}_2\text{O}$ (C) Decomposition reaction.
(iv) $2\text{Cu(NO}_3)_2\xrightarrow{\ \ \ \ \ \ \ \ \ \ }2\text{CuO}\ +\ 4\text{NO}_2\ +\ \text{O}_2$ (D) Combination reaction.
→
An object is placed at a distance of 60cm from a concave lens of focal length 30cm.
  1. Use lens formula to find the distance of the image from the lens.
  2. List four characteristics of the image (nature, position, size, erect/ inverted) formed by the lens in this case.
  3. Draw ray diagram to justify your answer of part (ii).
→