Question

Security inks exploit the same principle that causes the vivid and constantly changing colours of a film of oil on water.
A. When two rays of light meet each other after being reflected from these different surfaces, they have each travelled slightly different distances.
B. The key is that the light is bouncing off two surfaces, that of the oil and that of the water layer below it.
C. The distance the two travel determines which wavelengths and hence colours, interfere constructively and look bright.
D. Because light is an electromagnetic wave, the peaks and troughs of each ray then interfere either constructively to appear bright, or destructively, to appear dim.
6. Since the distance the rays travel changes with the angle as you look at the surface, different colours look bright from different viewing angles.

• A. ABCD
• B. BADC
• C. BDAC
• D. DCAB

Hint:

In scientific para-jumbles, arrange the sentences from mechanism → scientific principle → cause → observable effect for clarity.

Answer 1

The Correct Option is C

(B) follows the introductory sentence by identifying the two reflecting surfaces. (D) then explains the role of light as an electromagnetic wave and how interference occurs. (A) highlights the cause of interference — the difference in the distances travelled by the two rays. (C) concludes by linking the travel distance to wavelength and colour effects. This sequence presents the idea from mechanism to cause and final result in a coherent flow.