A thin vertical flat plate of height L, and infinite width perpendicular to the plane of the figure, is losing heat t o t he sur r oundi ngs by nat ur al convection. The temperature of the plate and the surroundings, and the proper ties of t he surrounding fluid, are constant. The relationship bet ween t he average Nussel t and Rayl ei gh numbers is given as Nu = K Ra

^{1/4}, where K is a constant. The lengt h scales for Nusselt and Rayleigh numbers are the height of the plate. The height of the plate is increased to 16L keeping all other factors constant

If the average heat transfer coefficient for the first plate is h

_{1} and that for the second plate is h

_{2}, the value of the ratio h

_{1} /h

_{2} is