(23. In Young's double slit experiment, total 63 fringes are seen in visible region for sodium light of wavelength \( 5893 \AA \). If violet light of wavelength \( 4358 \AA \) is used in place of sodium light, then total number of fringes seen will be \( n \). Find \( n \).

7. A train overtakes 2 persons walking \( 2 \mathrm{~km} / \mathrm{hr} \) and \( 4 \mathrm{~km} / \mathrm{hr} \) respectively in the same direction an completely passes them in 9 seconds and 10 seconds. What is the speed of the trains in \( \mathrm{km} / \mathrm{hr} \) ? \( \begin{array}{llll}\text { 1) } 13.2 & \text { 2) } 17.6 & \text { 3) } 22 & \text { 4) } 26.4\end{array} \)

6. A train moving at uniform speed takes 20 secs. to pass a cyclist riding at \( 11 \mathrm{~km} / \mathrm{hr} \) in the same direction as train but takes only 9 secs. to pass a post. What is the length of the train? \( \begin{array}{llll}\text { 1) } 50 \mathrm{~m} & \text { 2) } 60 \mathrm{~m} & \text { 3) } 70 \mathrm{~m} & \text { 4) } 80 \mathrm{~m}\end{array} \)

7. A train overtakes 2 persons walking \( 2 \mathrm{~km} / \mathrm{hr} \) and \( 4 \mathrm{~km} / \mathrm{hr} \) respectively in the same direction and completely passes them in 9 seconds and 10 seconds. What is the speed of the trains in \( \mathrm{km} / \mathrm{hr} \) ? \( \begin{array}{llll}\text { 1) } 13.2 & \text { 2) } 17.6 & \text { 3) } 22 & \text { 4) } 26.4\end{array} \)

2. Жасанды серік Жер бетінен 600 км биіктікте дөңгелек орбита бойымен айналуы үшін қандай жылдамды алуы керек? Оның айналу периоды қандай? [3]

4.Жердің жасанды серіктерінің қозғалысы қозғалыстың қандай түріне жатады.?