The correct answer is 104
\(400 = \frac{ν}{4(L_1+e)} ..... (i)\)
\(400 = \frac{5v}{4(L_2+e)} ..... (ii)\)
By using equation (i) and (ii) , we get
\(⇒ L1 + e = \frac{λ}{4} = 21 cm\)
\(L2 + e = \frac{5λ}{4} = 105 cm\)
⇒ e = 1 cm & L2 = 104 cm

Two positively charged particles \(m_1\) and \(m_2\) have been accelerated across the same potential difference of 200 keV. Given mass of \(m_1 = 1 \,\text{amu}\) and \(m_2 = 4 \,\text{amu}\). The de Broglie wavelength of \(m_1\) will be \(x\) times that of \(m_2\). The value of \(x\) is _______ (nearest integer). 
Sound is a vibration that propagates the mechanical wave of displacement and pressure, through a medium can be of any matter. In other words, the sound is the thin line between Music sound and Noise.
Sound can be divided into two types depending on its frequency. The following are:-