(a) Why do we use red colour as a danger signal on the top of a skyscraper?
(b) The diagram below shows the path of a blue ray through the prism:
(i) Calculate the critical angle of the material of the prism for blue colour.
(ii) What is the measure of the angle of this prism (A)?
(iii) Which colour should replace the blue ray, for the ray to undergo Total Internal Reflection?
(a) Red colour is used because it has the longest wavelength among visible light, so it is scattered the least and remains visible from a long distance.
(b) (i) At Q, angle of incidence = 133° − 90° = 43°. Hence, the critical angle is 43°.
(ii) In △APQ, 90° + 47° + ∠PAQ = 180°. Hence, ∠A = 43°.
(iii) Indigo should replace the blue ray because its wavelength is lower.
More ICSE Easy level questions
Below is an incomplete table showing the arrangement of electromagnetic spectrum in the increasing order of their wavelength. Complete the table. Gamma ray X-ray U V rays Visible rays Infrared A Radio waves (a) Identify the radiation A. (b) Name the radiation used to detect fracture in bones. (c) Name one property common to both A and Radio waves.
Assertion (A): Ultraviolet radiations are scattered more as compared to the microwave radiations. Reason (R): Wavelength of ultraviolet radiation is more than the wavelength of microwave radiation. (a) Both A and R are true. (b) A is true but R is false. (c) A is false but R is true. (d) Both A and R are false.
(a) Name the radiations: (1) for which a quartz prism is used to study the spectrum. (2) which are used in remote sensing devices. (3) which are used in traffic signals in India. (b) Name one property common to all electromagnetic radiations.
The diagram below shows the ray OP travelling through an equilateral prism of a certain material. (a) Calculate the value of i2, if the angle of deviation is 43°. (b) What is the ray QS called?
The diagram below shows two parallel rays A (Orange) & B (Blue) incident from air, on air-glass boundary. (a) Copy and complete the path of the rays A and B. (b) How do the speeds of these rays differ in glass?(c) Are the two refracted rays in glass parallel? Give a reason.
(a) Infrared radiations are used in warfare. Explain with reason, why. (b) A ray of light is incident at 45° on an equilateral prism in the diagram below. (1) Name the phenomenon exhibited by the ray of light when it enters and emerges out of the prism. (2) State the cause of the above phenomenon mentioned by you.
A blackened thermometer bulb placed beyond the red end of a spectrum shows a rise in temperature due to: (a) infrared radiations (b) ultraviolet radiations (c) X-rays (d) radio waves
Which one of the following combinations is the correct ascending order of electromagnetic waves in terms of wavelength? (a) Gamma-rays, visible light, microwaves (b) Microwaves, visible light, gamma-rays (c) Gamma-rays, microwaves, visible light (d) Microwaves, gamma-rays, visible light
Assertion: Tiny air molecules scatter blue light more than red light. Reason: The refractive index of air is greater for blue light than for red light. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. (b) Both Assertion and Reason are false. (c) Assertion is true but Reason is false. (d) Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
(a) Name the electromagnetic radiation used to detect fake currency. (b) Redraw the diagram given below and complete the path of the light ray AB through the glass prism till it emerges out of the prism. Critical angle of the glass is 42°.
(a) Define Centre of Gravity. (b) A hollow ice cream cone has height 6 cm. (i) Where is the position of its centre of gravity from the broad base? (ii) Will its position change when it is filled completely with honey? Write Yes or No.
Study the diagram: (a) Calculate the total resistance of the circuit. (b) Calculate the current drawn from the cell. (c) State whether the current through 10 Ω resistor is greater than, less than or equal to the current through the 12 Ω resistor.
