• Radio-cobalt 
• Radio-phosphorus
• Radio-gas
• Radio-carbon
• Radio-carbon

• Radiowaves, X-Rays, visible rays
• X-Rays, Visible rays, Radiowaves
• X-Rays, Y-Rays, Visible rays
• Visible rays, Y-rays, X-rays

• Velocity of light is constant in all media
• Velocity of light in vacuum is maximum
• Velocity of light is same in all reference frames
• Locus of nature have identical form in all reference frames

The velocity of light in vacuum can be changed by changing

• frequency
• amplitude
• wavelength
• None of these

• $\overrightarrow{\mathrm{B}} \times \overrightarrow{\mathrm{E}}$
• $\overrightarrow{\mathrm{E}} \times \overrightarrow{\mathrm{B}}$
• $\overrightarrow{\mathrm{E}}$
• $\overrightarrow{\mathrm{B}}$