# CBSE Class 10 Science Activities Part (4)

Complete the ‘inference statements,’ based on your interpretation of the data collecter by you, for a concave lens

a. the image is always ............................ in nature.

b. The image moves ........(nearer/away)............. to /from the focus as the object is moved progressively closer to the optical centre.

c. The image size keeps on progressively ........(decreasing/increasing) ............. as the object is moved progressively away from the focus.

d. For all object distances less than the focal length, the image is ........(diminished/ magnified) ............. with respect to the object.

Suggested Remediation :

The teacher may guide students about

● Choosing an ‘appropriate scale’ in each situation

● Drawing ‘to the scale’ ray diagrams

● Observing any regularity/pattern present is a (given) data

● Drawing conclusions on the basis of the observed regularity/pattern in the (given) data.

Human Eye and Colourful World Chapter 11

Assessment Technique: Application based work sheet.

Objective : To enable the student to learn about the

● approximate size (say, r,) of the (normal) eye-ball

● that, in case of human eye, the distance between the screen (the retina) and the eye-lens remains (nearly) fixed irrespective of the distance of the object

● That during normal relaxed vision, u = – ∞ and v = r.

● That for u ≈ – 25cm, and v = r, the eye is looking at an object kept at the least distance of distinct vision.

● That the amazing ‘power of accommodation’ of the human eye does not really involve a very large percentage change in the focal length of the eye-lens.

Task : Individual numerical problem

Assesment time: 20 Minutes

Procedure Task : The teacher may explain to the students that:

● size of the normal eye-ball may be taken as close to 2.0cm.

● object distance, during normal relaxed vision, of very far off objects, is infinite.

● minimum object distance, during the seeing of nearby objects, has to be (nearly) 25cm for the normal eye.

● Lens formula can be used to calculate the focal length of the eye-lens both for ‘far-off’ and for ‘near’ viewing.

● Power of a lens (in diopters) equals the reciprocal of the focal length (in meters).

Assessment Parameters : 1 mark for each correct answer.

Student Worksheet

Instructions : You are given that the size of the normal eyeball is nearly 2cm and the normal eye can adjust the focal length of its eye-lens to see objects situated anywhere from 25cm to an infinite distance away from it

Now answer the following questions:

1. What is the focal length (in metres) of the (normal) eye-lens when it is viewing a very far off object ?

2. What is the power of the eye-lens in this case ?

3. A normal eye is viewing an object kept 25cm away from it. What is the focal length of the eye-lens in this case ?

4. What is the power of the eye-lens for this (normal) near-viewing?

5. How much is the percentage change, in the focal length of the eye-lens, when it adjusts itself, from its normal relaxed position, to the position where the eye can see the ‘nearbyobject’ clearly?

Suggested Remediation: Some of the students may not understand that the size of the eye-ball is equal to the image distance irrespective of the position of the object. The teacher may help the students

● realize that in the case of the human eye, the distance between the lens and the screen (the retina) remains fixed and that this distance is (nearly) equal to the size of the eyeball.

(i) very far–off (ii) normal near–viewing.

● calculate the percentage change in the focal length of the eye-lens and appreciate that it is not a very large change.

● appreciate the wonderful capacity of the human eye—its amazing 'power of accommodation'

Human Eye and Colourful World Chapter 11

Assessent Technique: Individual Worksheet

Objective : To enable the learner to get familiar with

● some natural phenomenon based on the dispersion of light.

● places, time and situations under which these phenomenon are best observed

● The ways and means of presenting these observed phenomenon through suitable drawings/paintings/photographs

Assessment Task: Listing, Recapitulation, Drawing

Procedure : The teacher may discuss with the students

● about some natural phenomenon like the rainbow, the red colour of sky at sunset and sunrise times, the blue of sky - based on the multicolored nature of sun light.

● about cause/s – reflection, refraction, total internal reflection, scattering etc.- that are associated with these different phenomenon.

● to look for other interesting natural phenomenon through surfing the net, talking with seniors, reading from books etc.- that are associated with the multicoloured nature of white light.

● record their interesting observations through suitable (coloured) drawings/paintings/ photographs etc.

● to try and visit places, far from the haze and dust of crowded cities, for a clearer and better observation of these natural phenomenon.

Assessment Parameters : Two marks for listing of natural phenomenon

One mark for the recapitulation of the place or (approximate) time of their observations Two marks for (at least one) drawing/painting/photograph of the natural phenomenon observed.

Student Worksheet

Instructions: Do as directed:

1. Make a list of the natural phenomenon associated with the multicoloured nature of white light.

2. When and where did you observe/last observe (any one/some of) the phenomenon listed above?

3. Draw a drawing or make/collect a painting or give your own/otherwise availablephotograph of the natural phenomenon that you liked and appreciated the most.

Suggested Remediation :

● Some of the students may not be keen to study the phenomenon and collect relevant information/pictures of the same. The teacher may aruse their curiosity by explosive them to the wonderful world of natural phenomenon like the rainbow, the ‘red-colour’ of the sky at sun-rise and sun-set, the blue of the sky and so on.

● The teacher may also collect information- to the extent possible – from the net, books, newspaper and magazine reports – about some not so common phenomenon, based on the multicoloured nature of sunlight.

● The teacher may encourage and motivate her/his students to appreciate the boundless beauties and wonders of nature and to do their best to cause least damage to nature and natural surroundings.

Please refer to attached file for CBSE Class 10 Science Activities Part (4)

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