हिंदी

Give a scientific reason: Danger signal lights are red in colour.

Advertisements
Advertisements

प्रश्न

Give a scientific reason:

Danger signal lights are red in colour.

कारण बताइए
Advertisements

उत्तर

  1. The effectiveness of scattering depends on the size of the particles and the wavelength of the light.
  2. Red light has the longest wavelength in the visible spectrum; therefore, it is scattered the least by air molecules, fog, or smoke.
  3. Due to minimal scattering, red light travels longer distances without losing its intensity and can be clearly seen from far away.
Therefore, danger signal lights are red in colour.
shaalaa.com
  क्या इस प्रश्न या उत्तर में कोई त्रुटि है?
2014-2015 (March)

संबंधित प्रश्न

Name the phenomenon responsible for it.


Draw the intensity distribution for the fringes produced in interference ?


 Write two points of difference between the phenomena of interference and diffraction.


A convex lens is made of a material having refractive index
\[1 \cdot 2\] Both the surfaces of the lens are convex. If it is dipped into water (μ = 1.33), it will behave like 


A concave mirror having a radius of curvature 40 cm is placed in front of an illuminated point source at a distance of 30 cm from it. Find the location of the image.


A point source S is placed midway between two converging mirrors having equal focal length f as shown in figure. Find the values of d for which only one image is formed.


Locate the image of the point P as seen by the eye in the figure.


k transparent slabs are arranged one over another. The refractive indices of the slabs are μ1, μ2, μ3, ... μk and the thicknesses are t1 t2t3, ... tk. An object is seen through this combination with nearly perpendicular light. Find the equivalent refractive index of the system which will allow the image to be formed at the same place.


A cylindrical vessel, whose diameter and height both are equal to 30 cm, is placed on a horizontal surface and a small particle P is placed in it at a distance of 5.0 cm from the centre. An eye is placed at a position such that the edge of the bottom is just visible (see figure). The particle P is in the plane of drawing. Up to what minimum height should water be poured in the vessel to make the particle P visible?


An optical fibre (μ = 1.72) is surrounded by a glass coating (μ = 1.50). Find the critical angle for total internal reflection at the fibre-glass interface.


A biconvex thick lens is constructed with glass (μ = 1.50). Each of the surfaces has a radius of 10 cm and the thickness at the middle is 5 cm. Locate the image of an object placed far away from the lens.


Answer the following question in detail.

Explain the formation of a primary rainbow. For which angular range with the horizontal is it visible?


Answer the following question in detail.

Is it possible to see primary and secondary rainbow simultaneously? Under what conditions?


State any one difference between a primary rainbow and a secondary rainbow.


Explain the formation of primary and secondary rainbow.


Case study: Mirage in deserts 

To a distant observer, the light appears to be coming from somewhere below the ground. The observer naturally assumes that light is being reflected from the ground, say, by a pool of water near the tall object.

Such inverted images of distant tall objects cause an optical illusion to the observer. This phenomenon is called mirage. This type of mirage is especially common in hot deserts.

Based on the above facts, answer the following question:

Which of the following phenomena is prominently involved in the formation of mirage in deserts?


Case study: Mirage in deserts 

To a distant observer, the light appears to be coming from somewhere below the ground. The observer naturally assumes that light is being reflected from the ground, say, by a pool of water near the tall object.

Such inverted images of distant tall objects cause an optical illusion to the observer. This phenomenon is called mirage. This type of mirage is especially common in hot deserts.

Based on the above facts, answer the following question:

A diamond is immersed in such a liquid which has its refractive index with respect to air as greater than the refractive index of water with respect to air. Then the critical angle of diamond-liquid interface as compared to critical angle of diamond-water interface will


The sky would appear red instead of blue if


A short pulse of white light is incident from air to a glass slab at normal incidence. After travelling through the slab, the first colour to emerge is ______.


Between the primary and secondary rainbows, there is a dark band known as Alexandar’s dark band. This is because ______.

  1. light scattered into this region interfere destructively.
  2. there is no light scattered into this region.
  3. light is absorbed in this region.
  4. angle made at the eye by the scattered rays with respect to the incident light of the sun lies between approximately 42° and 50°.

Share
Notifications

Englishहिंदीमराठी


      Forgot password?
Use app×