Observe this beautiful figure . It is a symmetric pattern known as koch's snow flake ( If you have access to a computer , browse through the topic 'fractal ' and find more such beauties !) .Find the lines of symmetry in this figure .

5.20, AC and BE intersect at P. AC and BC intersect at C. AC and EC intersect at C. Try to find another ten pairs of intersecting line segments. Should any two lines or line segments necessarily intersect? Can you find two pairs of non-intersecting line segments in the figure? Can two lines intersect in more than one point? Think about it.

The Young's double-slit experiment is done in a medium of refractive index 4//3. A light of 600 nm wavelength is falling on the slits having 0.45 mm separation. The lower shift S_(2) is covered by a thin glass sheet of thickness 10.4 mm and refractive index. 1.5. The interference pattern is observed on a screen placed 1.5 m from the slits as shown in Figure Find the light intensity of point O relative to the maximum fringe intensity.

The Young's double-slit experiment is done in a medium of refractive index 4//3. A light of 600 nm wavelength is falling on the slits having 0.45 mm separation. The lower shift S_(2) is covered by a thin glass sheet of refractive index. 1.5. The interference pattern is observed on a screen placed 1.5 m from the slits as shown in Figure a. Find the location of central maximum (bright fringe with zero path difference) on the y-axis.