If `L_1&L_2` are the lengths of the segments of any focal chord of the parabola `y^2=x ,` then (a) `1/(L_1)+1/(L_2)=2` (b) `1/(L_1)+1/(L_2)=1/2` (c) `1/(L_1)+1/(L_2)=4` (d) `1/(L_1)+1/(L_2)=1/4`

The chord of contact of tangents from a point P to a circle passes through Qdot If l_1a n dl_2 are the length of the tangents from Pa n dQ to the circle, then P Q is equal to (l_1+l_2)/2 (b) (l_1-l_2)/2 sqrt(l1 2+l2 2) (d) 2sqrt(l1 2+l2 2)

Consider atoms H, He^(+), Li^(++) in their ground states. If L_(1), L_(2) and L_(3) are magnitude of angular momentum of their electrons about the nucleus respectively then: A. L_(1)=L_(2)=L_(3) B. L_(1) gt L_(2) gt L_(3) C. L_(1) lt L_(2) lt L_(3) D. L_(1)=L_(2)=L_(3)

For the given figure, which one is the mirror line, l_1 or l_2 ?

L_(1):(x+1)/(-3)=(y-3)/(2)=(z+2)/(1),L_(2):(x)/(1)=(y-7)/(-3)=(z+7)/(2) The lines L_(1) and L_(2) are -

If 'c' is small in comparison with l then ((l)/(l+c))^(1//2) + ((l)/(l-c))^(1//2) =

If l_(1), l_(2), l_(3) are respectively the perpendicular from the vertices of a triangle on the opposite side, then show that l_(1)l_(2) l_(3) =(a^(2)b ^(2) c^(2))/(8R^(3)).

If the lines L_1 and L_2 are tangents to 4x^2-4x-24 y+49=0 and are normals for x^2+y^2=72 , then find the slopes of L_1 and L_2dot

Explain giving reasons, which of the following sets of quantum numbers are not possible? (a) n=0, l=0, m_(l)=0, m_(s)=+1/2 (b) n=1, l=0, m_(l)=0, m_(s)=-1/2 (c) n=1, l=1, m_(l)=0, m_(s)=+1/2 (d) n=2, l=1, m_(l)=0, m_(s)=-1/2 (e) n=3, l=3, m_(l)=-3, m_(s)=+1/2 (f) n=3, l=1, m_(l)=0, m_(s)=+1/2

In Figure, if l_1||l_2 , what is the value of y ? (a) 100 (b) 120 (c) 135 (d) 150

Supose directioncoisnes of two lines are given by u l+vm+wn=0 and al^2+bm^2+cn^2=0 where u,v,w,a,b,c are arbitrary constnts and l,m,n are directioncosines of the lines. For u=v=w=1 if (n_1 n_2)/(l_1 l_2)=((a+b)/(b+c)) then (A) (m_1m_2)/(l_1 l_2)=((b+c))/((c+a)) (B) (m_1m_2)/(l_1 l_2)=((c+a))/((b+c)) (C) (m_1m_2)/(l_1 l_2)=((a+b))/((c+a)) (D) (m_1m_2)/(l_1 l_2)=((c+a))/((a+b))